Kuro is living in a country called Uberland, consisting of n towns, numbered from 1 to n, and n - 1 bidirectional roads connecting these towns. It is possible to reach each town from any other. Each road connects two towns a and b. Kuro loves walking and he is planning to take a walking marathon, in which he will choose a pair of towns (u, v) (u ≠ v) and walk from u using the shortest path to v (note that (u, v) is considered to be different from (v, u)).

Oddly, there are 2 special towns in Uberland named Flowrisa (denoted with the index x) and Beetopia (denoted with the index y). Flowrisa is a town where there are many strong-scent flowers, and Beetopia is another town where many bees live. In particular, Kuro will avoid any pair of towns (u, v) if on the path from u to v, he reaches Beetopia after he reached Flowrisa, since the bees will be attracted with the flower smell on Kuro’s body and sting him.

Kuro wants to know how many pair of city (u, v) he can take as his route. Since he’s not really bright, he asked you to help him with this problem.

Input

The first line contains three integers n, x and y (1 ≤ n ≤ 3 ⋅ 10^5, 1 ≤ x, y ≤ n, x ≠ y) - the number of towns, index of the town Flowrisa and index of the town Beetopia, respectively.

n - 1 lines follow, each line contains two integers a and b (1 ≤ a, b ≤ n, a ≠ b), describes a road connecting two towns a and b.

It is guaranteed that from each town, we can reach every other town in the city using the given roads. That is, the given map of towns and roads is a tree.

Output

A single integer resembles the number of pair of towns (u, v) that Kuro can use as his walking route.

Examples

Input

3 1 3
1 2
2 3


Output

5

Input

3 1 3
1 2
1 3


Output

4

Note

On the first example, Kuro can choose these pairs: 

  * (1, 2): his route would be 1 → 2, 
  * (2, 3): his route would be 2 → 3, 
  * (3, 2): his route would be 3 → 2, 
  * (2, 1): his route would be 2 → 1, 
  * (3, 1): his route would be 3 → 2 → 1. 



Kuro can't choose pair (1, 3) since his walking route would be 1 → 2 → 3, in which Kuro visits town 1 (Flowrisa) and then visits town 3 (Beetopia), which is not allowed (note that pair (3, 1) is still allowed because although Kuro visited Flowrisa and Beetopia, he did not visit them in that order).

On the second example, Kuro can choose the following pairs: 

  * (1, 2): his route would be 1 → 2, 
  * (2, 1): his route would be 2 → 1, 
  * (3, 2): his route would be 3 → 1 → 2, 
  * (3, 1): his route would be 3 → 1. 
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeSet;
import java.util.stream.Collectors;

public class Main {
    static int mod = (int) (1e9) + 7;

    /* ======================DSU===================== */
    static class dsu {
        static int parent[], n;// min[],value[];
        static long size[];

        dsu(int n) {
            parent = new int[n + 1];
            size = new long[n + 1];
            // min=new int[n+1];
            // value=new int[n+1];
            this.n = n;
            makeSet();
        }

        static void makeSet() {
            for (int i = 1; i <= n; i++) {
                parent[i] = i;
                size[i] = 1;
                // min[i]=i;
            }
        }

        static int find(int a) {
            if (parent[a] == a)
                return a;
            else {
                return parent[a] = find(parent[a]);// Path Compression
            }
        }

        static void union(int a, int b) {
            int setA = find(a);
            int setB = find(b);
            if (setA == setB)
                return;
            if (size[setA] >= size[setB]) {
                parent[setB] = setA;
                size[setA] += size[setB];
            } else {
                parent[setA] = setB;
                size[setB] += size[setA];
            }
        }
    }

    /* ======================================================== */
    static class Pair<X extends Number, Y extends Number> implements Comparator<Pair> {
        X x;
        Y y;

        // Constructor
        public Pair(X x, Y y) {
            this.x = x;
            this.y = y;
        }

        public Pair() {

        }

        @Override
        public int compare(Main.Pair o1, Main.Pair o2) {
            return ((int) (o1.y.intValue() - o2.y.intValue()));// Ascending Order based on 'y'
        }
    }

    /* ===============================Tries================================= */
    static class TrieNode {
        private HashMap<Character, TrieNode> children = new HashMap<>();
        public int size;
        boolean endOfWord;

        public void putChildIfAbsent(char ch) {
            children.putIfAbsent(ch, new TrieNode());
        }

        public TrieNode getChild(char ch) {
            return children.get(ch);
        }
    }

    static private TrieNode root;

    public static void insert(String str) {
        TrieNode curr = root;
        for (char ch : str.toCharArray()) {
            curr.putChildIfAbsent(ch);
            curr = curr.getChild(ch);
            curr.size++;
        }
        // mark the current nodes endOfWord as true
        curr.endOfWord = true;
    }

    public static int search(String word) {
        TrieNode curr = root;

        for (char ch : word.toCharArray()) {
            curr = curr.getChild(ch);
            if (curr == null) {
                return 0;
            }
        }
        // size contains words starting with prefix- word
        return curr.size;
    }

    public boolean delete(TrieNode current, String word, int index) {
        if (index == word.length()) {
            // when end of word is reached only delete if currrent.endOfWord is true.
            if (!current.endOfWord) {
                return false;
            }
            current.endOfWord = false;
            // if current has no other mapping then return true
            return current.children.size() == 0;
        }
        char ch = word.charAt(index);
        TrieNode node = current.children.get(ch);
        if (node == null) {
            return false;
        }
        boolean shouldDeleteCurrentNode = delete(node, word, index + 1);

        // if true is returned then delete the mapping of character and trienode
        // reference from map.
        if (shouldDeleteCurrentNode) {
            current.children.remove(ch);
            // return true if no mappings are left in the map.
            return current.children.size() == 0;
        }
        return false;
    }

    /* ================================================================= */
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

        int[] intArr(int n) {
            int res[] = new int[n];
            for (int i = 0; i < n; i++)
                res[i] = nextInt();
            return res;
        }

        long[] longArr(int n) {
            long res[] = new long[n];
            for (int i = 0; i < n; i++)
                res[i] = nextLong();
            return res;
        }
    }

    static FastReader f = new FastReader();
    static BufferedWriter w = new BufferedWriter(new OutputStreamWriter(System.out));

    static boolean isPrime(long n) {
        if (n <= 1)
            return false;
        if (n <= 3)
            return true;
        if (n % 2 == 0 || n % 3 == 0)
            return false;
        for (long i = 5; i * i <= n; i = i + 6)
            if (n % i == 0 || n % (i + 2) == 0)
                return false;
        return true;
    }

    static int lowerBound(int a[], int x) { // x is the target, returns lowerBound. If not found return -1
        int l = -1, r = a.length, flag = 0;
        while (l + 1 < r) {
            int m = (l + r) >>> 1;
            if (x == a[m])
                flag = 1;
            if (a[m] >= x)
                r = m;
            else
                l = m;
        }
        return r;
    }

    static int upperBound(int a[], int x) {// x is the target, returns upperBound. If not found return -1
        int l = -1, r = a.length, flag = 0;
        while (l + 1 < r) {
            int m = (l + r) >>> 1;
            if (a[m] == x)
                flag = 1;
            if (a[m] <= x)
                l = m;
            else
                r = m;
        }
        return (l + 1);
    }

    static long gcd(long a, long b) {
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }

    static long lcm(long a, long b) {
        return (a * b) / gcd(a, b);
    }

    static long power(long x, long y) {
        long res = 1;
        while (y > 0) {
            if (y % 2 == 1)
                res = (res * x);
            y >>= 1;
            x = (x * x);
        }
        return res;
    }

    public double binPow(double x, int n) {// binary exponentiation with negative power as well
        if (n == 0)
            return 1.0;
        double binPow = binPow(x, n / 2);
        if (n % 2 == 0) {
            return binPow * binPow;
        } else {
            return n > 0 ? (binPow * binPow * x) : (binPow * binPow / x);
        }
    }

    static long ceil(long x, long y) {
        return (x % y == 0 ? x / y : (x / y + 1));
    }

    /*
     * ===========Modular Operations==================
     */
    static long modPower(long x, long y, long p) {
        long res = 1;
        x = x % p;
        while (y > 0) {
            if (y % 2 == 1)
                res = (res * x) % p;
            y = y >> 1; // y = y/2
            x = (x * x) % p;
        }
        return res;
    }

    static long modInverse(long n, long p) {
        return modPower(n, p - 2, p);
    }

    static long modAdd(long a, long b) {
        return ((a + b + mod) % mod);
    }

    static long modMul(long a, long b) {
        return ((a % mod) * (b % mod)) % mod;
    }

    static long nCrModPFermat(int n, int r) {
        if (r == 0)
            return 1;
        long[] fac = new long[n + 1];
        fac[0] = 1;
        for (int i = 1; i <= n; i++)
            fac[i] = fac[i - 1] * i % mod;
        return (fac[n] * modInverse(fac[r], mod) % mod * modInverse(fac[n - r], mod) % mod) % mod;
    }

    /*
     * ===============================================
     */

    static void ruffleSort(long[] a) {
        int n = a.length;
        Random r = new Random();
        for (int i = 0; i < a.length; i++) {
            int oi = r.nextInt(n);
            long temp = a[i];
            a[i] = a[oi];
            a[oi] = temp;
        }
        Arrays.sort(a);
    }

    static void ruffleSort(int[] a) {
        int n = a.length;
        Random r = new Random();
        for (int i = 0; i < a.length; i++) {
            int oi = r.nextInt(n);
            int temp = a[i];
            a[i] = a[oi];
            a[oi] = temp;
        }
        Arrays.sort(a);
    }

    static String binString32(int n) {
        StringBuilder str = new StringBuilder("");
        String bin = Integer.toBinaryString(n);
        if (bin.length() != 32) {
            for (int k = 0; k < 32 - bin.length(); k++) {
                str.append("0");
            }
            str.append(bin);
        }
        return str.toString();
    }

    static class sparseTable {
        public static int st[][];
        public static int log = 4;

        static int func(int a, int b) {// make func as per question(here min range query)
            return (int) gcd(a, b);
        }

        void makeTable(int n, int a[]) {

            st = new int[n][log];
            for (int i = 0; i < n; i++) {
                st[i][0] = a[i];
            }
            for (int j = 1; j < log; j++) {
                for (int i = 0; i + (1 << j) <= n; i++) {
                    st[i][j] = func(st[i][j - 1], st[i + (1 << (j - 1))][j - 1]);
                }
            }
        }

        static int query(int l, int r) {
            int length = r - l + 1;
            int k = 0;
            while ((1 << (k + 1)) <= length) {
                k++;
            }
            return func(st[l][k], st[r - (1 << k) + 1][k]);
        }

        static void printTable(int n) {
            for (int j = 0; j < log; j++) {
                for (int i = 0; i < n; i++) {
                    System.out.print(st[i][j] + " ");
                }
                System.out.println();
            }
        }
    }

    /*
     * ====================================Main=================================
     */

    // static int st[], a[];

    // static void buildTree(int treeIndex, int lo, int hi) {
    // if (hi == lo) {
    // st[treeIndex] = a[lo];
    // return;
    // }
    // int mid = (lo + hi) / 2;
    // buildTree(treeIndex * 2 + 1, lo, mid);
    // buildTree(treeIndex * 2 + 2, mid + 1, hi);
    // st[treeIndex] = merge(st[treeIndex * 2 + 1], st[treeIndex * 2 + 2]);
    // }

    // static void update(int treeIndex, int lo, int hi, int arrIndex, int val) {
    // if (hi == lo) {
    // st[treeIndex] = val;
    // a[arrIndex] = val;
    // return;
    // }
    // int mid = (hi + lo) / 2;
    // if (mid < arrIndex) {
    // update(treeIndex * 2 + 2, mid + 1, hi, arrIndex, val);
    // } else {
    // update(treeIndex * 2 + 1, lo, mid, arrIndex, val);
    // }
    // st[treeIndex] = merge(st[treeIndex * 2 + 1], st[treeIndex * 2 + 2]);
    // }

    // static int query(int treeIndex, int lo, int hi, int l, int r) {
    // if (l <= lo && r >= hi) {
    // return st[treeIndex];
    // }
    // if (l > hi || r < lo) {
    // return 0;
    // }
    // int mid = (hi + lo) / 2;
    // return query(treeIndex * 2 + 1, lo, mid, l, Math.min(mid, r));
    // }

    // static int merge(int a, int b) {
    // return a + b;
    // }

    public static long findKthPositive(long[] A, long k) {
        int l = 0, r = A.length, m;
        while (l < r) {
            m = (l + r) / 2;
            if (A[m] - 1 - m < k)
                l = m + 1;
            else
                r = m;
        }
        return l + k;
    }

    static int[] z_function(char ar[]) {
        int[] z = new int[ar.length];
        z[0] = ar.length;
        int l = 0;
        int r = 0;
        for (int i = 1; i < ar.length; i++) {
            if (r < i) {
                l = i;
                r = i;
                while (r < ar.length && ar[r - l] == ar[r])
                    r++;
                z[i] = r - l;
                r--;
            } else {
                int k = i - l;
                if (z[k] < r - i + 1) {
                    z[i] = z[k];
                } else {
                    l = i;
                    while (r < ar.length && ar[r - l] == ar[r])
                        r++;
                    z[i] = r - l;
                    r--;
                }
            }
        }
        return z;
    }

    static long dp[][][];
    static ArrayList<ArrayList<Integer>> g;
    static int numChild[],parent[];
    public static void main(String args[]) throws Exception {
        // File file = new File("D:\\VS Code\\Java\\Output.txt");
        // FileWriter fw = new FileWriter("D:\\VS Code\\Java\\Output.txt");
        int t = 1;
        // t = f.nextInt();
        int tc = 1;
        while (t-- != 0) {
            // BufferedReader br = new BufferedReader(new FileReader("PHOBIA.INP"));
            // PrintWriter pw = new PrintWriter(new BufferedWriter(new
            // FileWriter("PHOBIA.OUT")));
            int n=f.nextInt();
            int x=f.nextInt();
            int y=f.nextInt();
            g=new ArrayList<>();
            for(int i=0;i<=n;i++){
                g.add(new ArrayList<>());
            }
            for(int i=0;i<n-1;i++){
                int u,v;
                u=f.nextInt();
                v=f.nextInt();
                g.get(u).add(v);
                g.get(v).add(u);
            }
            long tot=(n*1l*(n-1));
            numChild=new int[n+1];
            parent=new int[n+1];
            Arrays.fill(numChild, 1);
            dfs(x,0,1);
            int p=y;
            while(parent[p]!=x){
                p=parent[p];
            }
            // System.out.println(p+" "+numChild[y]);
            long k=(n-numChild[y])*1l*numChild[y]-numChild[y]*1l*(numChild[p]-numChild[y]);
            w.write((tot-k)+"\n");
        }
        w.flush();
    }
    static void dfs(int node,int p,int h){
        parent[node]=p;
        for(int i:g.get(node)){
            if(i!=p){
                dfs(i, node, h+1);
                numChild[node]+=numChild[i];
            }
        }
    }
}
/*

 */