As you know, an undirected connected graph with n nodes and n - 1 edges is called a tree. You are given an integer d and a tree consisting of n nodes. Each node i has a value ai associated with it.

We call a set S of tree nodes valid if following conditions are satisfied:

  1. S is non-empty.
  2. S is connected. In other words, if nodes u and v are in S, then all nodes lying on the simple path between u and v should also be presented in S.
  3. <image>.



Your task is to count the number of valid sets. Since the result can be very large, you must print its remainder modulo 1000000007 (109 + 7).

Input

The first line contains two space-separated integers d (0 ≤ d ≤ 2000) and n (1 ≤ n ≤ 2000).

The second line contains n space-separated positive integers a1, a2, ..., an(1 ≤ ai ≤ 2000).

Then the next n - 1 line each contain pair of integers u and v (1 ≤ u, v ≤ n) denoting that there is an edge between u and v. It is guaranteed that these edges form a tree.

Output

Print the number of valid sets modulo 1000000007.

Examples

Input

1 4
2 1 3 2
1 2
1 3
3 4


Output

8


Input

0 3
1 2 3
1 2
2 3


Output

3


Input

4 8
7 8 7 5 4 6 4 10
1 6
1 2
5 8
1 3
3 5
6 7
3 4


Output

41

Note

In the first sample, there are exactly 8 valid sets: {1}, {2}, {3}, {4}, {1, 2}, {1, 3}, {3, 4} and {1, 3, 4}. Set {1, 2, 3, 4} is not valid, because the third condition isn't satisfied. Set {1, 4} satisfies the third condition, but conflicts with the second condition.
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.StringTokenizer;


public class Solution{
    
    ///////////////////////////////////////////////////////////////////////////
    static class FastScanner{
        BufferedReader s;
        StringTokenizer st;
        
        public FastScanner(InputStream InputStream){
            st = new StringTokenizer("");
            s = new BufferedReader(new InputStreamReader(InputStream));
        }
        
        public FastScanner(File f) throws FileNotFoundException{
            st = new StringTokenizer("");
            s = new BufferedReader (new FileReader(f));
        }
        
        public int nextInt() throws IOException{
            if(st.hasMoreTokens())
                return Integer.parseInt(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextInt();
            }
        }
        
/*      public double nextDouble() throws IOException{
            if(st.hasMoreTokens())
                return Double.parseDouble(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextDouble();
            }
        }
*/      
        public long nextLong() throws IOException{
            if(st.hasMoreTokens())
                return Long.parseLong(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextLong();
            }
        }
        
        public String nextString() throws IOException{
            if(st.hasMoreTokens())
                return st.nextToken();
            else{
                st = new StringTokenizer(s.readLine());
                return nextString();
            }
            
        }
        public String readLine() throws IOException{
            return s.readLine();
        }
        
        public void close() throws IOException{
            s.close();
        }
        
    }
    
    ////////////////////////////////////////////////////////////////////
    //      Number Theory
    
    long pow(long a,long b,long mod){
        long x = 1; long y = a;
        while(b > 0){
            if(b % 2 == 1){
                x = (x*y);
                x %= mod;
            }
            y = (y*y);
            y %= mod;
            b /= 2;         
        }
        return x;
    }
    
    int divisor(long x,long[] a){
        long limit = x;
        int numberOfDivisors = 0;

        for (int i=1; i < limit; ++i) {
            if (x % i == 0) {
                limit = x / i;
                if (limit != i) {
                    numberOfDivisors++;
                }
                numberOfDivisors++;
            }
        }
        return numberOfDivisors;
    }
    
    void findSubsets(int array[]){
        
        long numOfSubsets = 1 << array.length; 
        for(int i = 0; i < numOfSubsets; i++){
                
            int pos = array.length - 1;
            int bitmask = i;

            while(bitmask > 0){     
                if((bitmask & 1) == 1)
                    ww.print(array[pos]+" ");
                
                bitmask >>= 1;
                pos--;
            }

            ww.println();
        }
    }
    
    
    public static long gcd(long a, long b){
        return b == 0 ? a : gcd(b,a%b);
    }
    
  
    public static int lcm(int a,int b, int c){
        return lcm(lcm(a,b),c);
    }
    
    public static int lcm(int a, int b){
        return (int) (a*b/gcd(a,b));
    }
    
    ////////////////////////////////////////////////////////////////////
    
    
//    private static    FastScanner s = new FastScanner(new File("input.txt"));
//    private static PrintWriter ww = new PrintWriter(new FileWriter("output.txt"));
    static InputStream inputStream = System.in;
    static FastScanner s = new FastScanner(inputStream); 
    static OutputStream outputStream = System.out;
    static PrintWriter ww = new PrintWriter(new OutputStreamWriter(outputStream));
//      private static Scanner s = new Scanner(System.in);
    @SuppressWarnings("unused")
    private static int[][] states = { {-1,0} , {1,0} , {0,-1} , {0,1} };
    
      
    //////////////////////////////////////////////////////////////////// 
      
     
    public static void main(String[] args) throws IOException{
        new Solution().solve();
        s.close();
        ww.close();
    }
    
    
    ////////////////////////////////////////////////////////////////////
    
    int MAXN = 2000 + 10;
    int MOD = (int)(1e9) + 7;
    @SuppressWarnings("unchecked")
    ArrayList<Integer>[] adj = new ArrayList[MAXN];
    int[] a = new int[MAXN];
    long[] f = new long[MAXN];
    boolean[] visited = new boolean[MAXN];
    int d,n;
    
    void DFS(int u, int root) {
        visited[u] = true;
        f[u] = 1;
        for(int v : adj[u]) {
            if (!visited[v]) {
                if ((a[v] < a[root]) || (a[v] > a[root] + d)) continue;
                if ((a[v] == a[root]) && (v < root)) continue; // avoid duplicate counting
                DFS(v, root);
                f[u] = ((long)(f[u]) * (f[v] + 1)) % MOD;
            }
        }
    }
   
    
    void solve() throws IOException{
        
        d = s.nextInt();
        n = s.nextInt();
        
        for(int i=1;i<=n;i++) a[i] = s.nextInt();
        for(int i=0;i<adj.length;i++) adj[i] = new ArrayList<Integer>();
        for(int i=1;i<=n-1;i++){
            int u = s.nextInt();
            int v = s.nextInt();
            adj[u].add(v);
            adj[v].add(u);
        }
        
        long result = 0;
        for(int i = 1; i <= n; i++) {
            Arrays.fill(visited, false);
            Arrays.fill(f, 0);
            DFS(i, i);
//          ww.println(f[i]);
            result = (result + f[i]) % MOD;
        }
        ww.println(result);
    }
}