Luba needs your help again! Luba has n TV sets. She knows that i-th TV set will be working from moment of time li till moment ri, inclusive.

Luba wants to switch off one of TV sets in order to free the socket. Let's call some TV set redundant if after switching it off the number of integer moments of time when at least one of TV sets is working won't decrease. Luba will be very upset if she has to switch off a non-redundant TV set.

Help Luba by telling her the index of some redundant TV set. If there is no any, print -1.

Input

The first line contains one integer number n (1 ≤ n ≤ 2·105) — the number of TV sets.

Then n lines follow, each of them containing two integer numbers li, ri (0 ≤ li ≤ ri ≤ 109) denoting the working time of i-th TV set.

Output

If there is no any redundant TV set, print -1. Otherwise print the index of any redundant TV set (TV sets are indexed from 1 to n).

If there are multiple answers, print any of them.

Examples

Input

3
1 3
4 6
1 7


Output

1


Input

2
0 10
0 10


Output

1


Input

3
1 2
3 4
6 8


Output

-1


Input

3
1 2
2 3
3 4


Output

2

Note

Consider the first sample. Initially all integer moments of time such that at least one TV set is working are from the segment [1;7]. It's easy to see that this segment won't change if we switch off the first TV set (or the second one).

Note that in the fourth sample you can switch off the second TV set, since even without it all integer moments such that any of the TV sets is working denote the segment [1;4].
	                                                    import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.TreeMap;
import java.util.TreeSet;


	                 
	                 
	                 
	                 
	                 
	                public class Solution2 implements Runnable
	                {
	                    static final long MAX = 464897L;
	                    static class InputReader
	                    {
	                        private InputStream stream;
	                        private byte[] buf = new byte[1024];
	                        private int curChar;
	                        private int numChars;
	                        private SpaceCharFilter filter;
	                        private BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	                 
	                        public InputReader(InputStream stream)
	                        {
	                            this.stream = stream;
	                        }
	                        
	                        public int read()
	                        {
	                            if (numChars==-1) 
	                                throw new InputMismatchException();
	                            
	                            if (curChar >= numChars)
	                            {
	                                curChar = 0;
	                                try 
	                                {
	                                    numChars = stream.read(buf);
	                                }
	                                catch (IOException e)
	                                {
	                                    throw new InputMismatchException();
	                                }
	                                
	                                if(numChars <= 0)                
	                                    return -1;
	                            }
	                            return buf[curChar++];
	                        }
	                     
	                        public String nextLine()
	                        {
	                            String str = "";
	                            try
	                            {
	                                str = br.readLine();
	                            }
	                            catch (IOException e)
	                            {
	                                e.printStackTrace();
	                            }
	                            return str;
	                        }
	                        public int nextInt()
	                        {
	                            int c = read();
	                            
	                            while(isSpaceChar(c)) 
	                                c = read();
	                            
	                            int sgn = 1;
	                            
	                            if (c == '-') 
	                            {
	                                sgn = -1;
	                                c = read();
	                            }
	                            
	                            int res = 0;
	                            do 
	                            {
	                                if(c<'0'||c>'9') 
	                                    throw new InputMismatchException();
	                                res *= 10;
	                                res += c - '0';
	                                c = read();
	                            }
	                            while (!isSpaceChar(c)); 
	                            
	                            return res * sgn;
	                        }
	                        
	                        public long nextLong() 
	                        {
	                            int c = read();
	                            while (isSpaceChar(c))
	                                c = read();
	                            int sgn = 1;
	                            if (c == '-') 
	                            {
	                                sgn = -1;
	                                c = read();
	                            }
	                            long res = 0;
	                            
	                            do 
	                            {
	                                if (c < '0' || c > '9')
	                                    throw new InputMismatchException();
	                                res *= 10;
	                                res += c - '0';
	                                c = read();
	                            }
	                            while (!isSpaceChar(c));
	                                return res * sgn;
	                        }
	                        
	                        public double nextDouble() 
	                        {
	                            int c = read();
	                            while (isSpaceChar(c))
	                                c = read();
	                            int sgn = 1;
	                            if (c == '-') 
	                            {
	                                sgn = -1;
	                                c = read();
	                            }
	                            double res = 0;
	                            while (!isSpaceChar(c) && c != '.') 
	                            {
	                                if (c == 'e' || c == 'E')
	                                    return res * Math.pow(10, nextInt());
	                                if (c < '0' || c > '9')
	                                    throw new InputMismatchException();
	                                res *= 10;
	                                res += c - '0';
	                                c = read();
	                            }
	                            if (c == '.') 
	                            {
	                                c = read();
	                                double m = 1;
	                                while (!isSpaceChar(c)) 
	                                {
	                                    if (c == 'e' || c == 'E')
	                                        return res * Math.pow(10, nextInt());
	                                    if (c < '0' || c > '9')
	                                        throw new InputMismatchException();
	                                    m /= 10;
	                                    res += (c - '0') * m;
	                                    c = read();
	                                }
	                            }
	                            return res * sgn;
	                        }
	                        
	                        public String readString() 
	                        {
	                            int c = read();
	                            while (isSpaceChar(c))
	                                c = read();
	                            StringBuilder res = new StringBuilder();
	                            do 
	                            {
	                                res.appendCodePoint(c);
	                                c = read();
	                            } 
	                            while (!isSpaceChar(c));
	                            
	                            return res.toString();
	                        }
	                     
	                        public boolean isSpaceChar(int c) 
	                        {
	                            if (filter != null)
	                                return filter.isSpaceChar(c);
	                            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	                        }
	                     
	                        public String next() 
	                        {
	                            return readString();
	                        }
	                        
	                        public interface SpaceCharFilter 
	                        {
	                            public boolean isSpaceChar(int ch);
	                        }
	                    }
	                     
	                    public static void main(String args[]) throws Exception
	                    {
	                        new Thread(null, new Solution2(),"Solution2",1<<26).start();
	                    }   
	                    static long gcd(long a, long b) 
	                    { 
	                      if (b == 0) 
	                        return a; 
	                      return gcd(b, a % b);  
	                    } 
	                    static long lcm(long a,long b) {
	                        return (a*b)/gcd(a,b);
	                    }
	                    int maxn = 1000005;
	                    long MOD = 998244353;
	                    long prime = 29;
	                    TreeMap<Long,Long> dp = new TreeMap();
	                    TreeMap<Integer,ArrayList<Integer>> tree = new TreeMap();
	                    int[] val;
	                    int[] ans;
	                    
	                    long[] arr;
	                    public void run() 
	                    {
	                        InputReader sc = new InputReader(System.in);
	                        PrintWriter w = new PrintWriter(System.out);
	                        int n = sc.nextInt();
	                        Pair[] p = new Pair[n];
	                        for(int i = 0;i < n;i++) {
	                        	int l = sc.nextInt()-1;
	                        	int r = sc.nextInt()-1;
	                        	p[i] = new Pair(l,r,1);
	                        }
	                        //Arrays.sort(p);
	                        TreeMap<Integer,Integer> compress = new TreeMap();
	                        int num = 0;
	                        TreeSet<Integer> temp  =new TreeSet();
	                        for(int i = 0;i < n;i++) {
	                        	int[] x = {p[i].a,p[i].b,p[i].b + 1};
	                        	for(int j = 0;j < x.length;j++) {
	                        		temp.add(x[j]);
	                        	}
	                        }
	                        for(Integer val: temp) {
	                        	compress.put(val,num++);
	                        }
	                        prefix = new int[600005];
	                        segTree = new int[4*prefix.length];
	                        int[] arr = new int[600005];
	                        for(int i = 0;i < n;i++) {
	                        	int one = compress.get(p[i].a);
	                        	int two = compress.get(p[i].b + 1);
	                        	arr[one]++;
	                        	arr[two]--;
	                        }
	                        prefix[0] = arr[0];
	                        for(int i  = 1;i < prefix.length;i++) {
	                        	prefix[i] = prefix[i-1] + arr[i];
	                        }
	                        build(0,prefix.length-1,0);
	                        for(int i = 0;i < n;i++) {
	                        	int one = compress.get(p[i].a);
	                        	int two = compress.get(p[i].b);
	                        	int quer = query(0,prefix.length-1,one,two,0);
	                        	if(quer > 1) {
	                        		w.println((i+1));
	                        		w.close();
	                        		System.exit(0);
	                        	}
	                        }
	                        w.println("-1");
	                        w.close();
	                    } 
	                    int[] prefix;
	                    int[] segTree;
	                    void build(int l,int r,int pos) {
	                    	if(l == r) {
	                    		segTree[pos] = prefix[l];
	                    		return;
	                    	}
	                    	int mid = (l + r)/2;
	                    	build(l,mid,2*pos+1);
	                    	build(mid+1,r,2*pos+2);
	                    	segTree[pos] = Math.min(segTree[2*pos+1],segTree[2*pos+2]);
	                    }
	                    int query(int l,int r,int start,int end,int pos) {
	                    	if(l > r || l >end || r < start) {
	                    		return Integer.MAX_VALUE;
	                    	}
	                    	if(l >= start && r <= end) {
	                    		return segTree[pos];
	                    	}
	                    	int mid = (l + r)/2;
	                    	int p1 = query(l,mid,start,end,2*pos+1);
	                    	int p2 = query(mid+1,r,start,end,2*pos+2);
	                    	return Math.min(p1,p2);
	                    }
	                    boolean isVowel(char ch) {
	                    	if(ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
	                    		return true;
	                    	}
	                    	return false;
	                    }
	                    static long power(long a,long b,long mod) {
                            long ans = 1;
                            a = a % mod;
                            while(b != 0) {
                                if(b % 2 == 1) {
                                    ans = (ans * a) % mod;
                                }
                                a = (a * a) % mod;
                                b = b/2;
                            }
                            return ans;
                        }
	                    class Pair implements Comparable<Pair>{
	                        int a;
	                        int b;
	                        int c;
	                        Pair(int a,int b,int c){
	                            this.b = b;
	                            this.a = a;
	                            this.c = c;
	                        }
	                        public boolean equals(Object o) {
	                            Pair p = (Pair)o;
	                            return this.a == p.a && this.b == this.b;
	                        }
	                        public int hashCode(){
	                            return Long.hashCode(a)*27 + Long.hashCode(b)*31;
	                        }
	                        public int compareTo(Pair p) {
	                        	if(this.a == p.a) {
	                        		return Long.compare(p.b, this.b);
	                        	}
	                            return Long.compare(this.a,p.a);
	                        }
	                    }
	                    
	                }