A coordinate line has n segments, the i-th segment starts at the position li and ends at the position ri. We will denote such a segment as [li, ri].

You have suggested that one of the defined segments covers all others. In other words, there is such segment in the given set, which contains all other ones. Now you want to test your assumption. Find in the given set the segment which covers all other segments, and print its number. If such a segment doesn't exist, print -1.

Formally we will assume that segment [a, b] covers segment [c, d], if they meet this condition a ≤ c ≤ d ≤ b. 

Input

The first line contains integer n (1 ≤ n ≤ 105) — the number of segments. Next n lines contain the descriptions of the segments. The i-th line contains two space-separated integers li, ri (1 ≤ li ≤ ri ≤ 109) — the borders of the i-th segment.

It is guaranteed that no two segments coincide.

Output

Print a single integer — the number of the segment that covers all other segments in the set. If there's no solution, print -1.

The segments are numbered starting from 1 in the order in which they appear in the input.

Examples

Input

3
1 1
2 2
3 3


Output

-1


Input

6
1 5
2 3
1 10
7 10
7 7
10 10


Output

3
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Random;
import java.util.StringTokenizer;

public class A {

	public static void main(String[] args) throws IOException {

		FastScanner sc = new FastScanner();
		int n = sc.nextInt();
		ArrayList<intpair> lis = new ArrayList<A.intpair>();
		int min = Integer.MAX_VALUE,max = -1;
		for(int i=1; i<=n; i++) {
			int a = sc.nextInt(),b = sc.nextInt();
			lis.add(new intpair(a,b));
			min = min(min,a);
			max = max(max,b);
		}
		int i=1;
		for(intpair e : lis) {
			if(e.x == min && e.y == max) {
				System.out.println(i);
				return;
			}
			i++;
		}
		System.out.println(-1);
		

	}

	static class FastScanner {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer("");

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

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

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

		long[] readArrayLong(int n) {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}

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

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

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

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

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

	static int max(int x, int y) {
		return Math.max(x, y);
	}

	static int min(int x, int y) {
		return Math.min(x, y);
	}

	static long max(long x, long y) {
		return Math.max(x, y);
	}

	static long min(long x, long y) {
		return Math.min(x, y);
	}

	static int min(int a[]) {
		int x = 1_000_000_00_9;
		for (int i = 0; i < a.length; i++)
			x = min(x, a[i]);
		return x;
	}

	static int max(int a[]) {
		int x = -1_000_000_00_9;
		for (int i = 0; i < a.length; i++)
			x = max(x, a[i]);
		return x;
	}

	static long min(long a[]) {
		long x = (long) 3e18;
		for (int i = 0; i < a.length; i++)
			x = min(x, a[i]);
		return x;
	}

	static long max(long a[]) {
		long x = -(long) 3e18;
		for (int i = 0; i < a.length; i++)
			x = max(x, a[i]);
		return x;
	}

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

	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;
	}

	static void intsort(int[] a) {
		List<Integer> temp = new ArrayList<Integer>();
		for (int i = 0; i < a.length; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		for (int i = 0; i < a.length; i++)
			a[i] = temp.get(i);
	}

	static void longsort(long[] a) {
		List<Long> temp = new ArrayList<Long>();
		for (int i = 0; i < a.length; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		for (int i = 0; i < a.length; i++)
			a[i] = temp.get(i);
	}

	static void reverseintsort(int[] a) {
		List<Integer> temp = new ArrayList<Integer>();
		for (int i = 0; i < a.length; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		Collections.reverseOrder();
		for (int i = 0; i < a.length; i++)
			a[i] = temp.get(i);
	}

	static void reverselongsort(long[] a) {
		List<Long> temp = new ArrayList<Long>();
		for (int i = 0; i < a.length; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		Collections.reverseOrder();
		for (int i = 0; i < a.length; i++)
			a[i] = temp.get(i);
	}

	static class longpair implements Comparable<longpair> {
		long x, y;

		longpair(long x, long y) {
			this.x = x;
			this.y = y;
		}

		public int compareTo(longpair p) {
			return Long.compare(this.x, p.x);
		}
	}

	static class intpair implements Comparable<intpair> {
		int x, y;

		intpair(int x, int y) {
			this.x = x;
			this.y = y;
		}

		@Override
		public int compareTo(intpair o) {
			return Integer.compare(this.x, o.x);
		}

		//		a = new pair [n];
		//		a[i] = new pair(coo,cost);

	}

	public static int gcd(int a, int b) {
		BigInteger b1 = BigInteger.valueOf(a);
		BigInteger b2 = BigInteger.valueOf(b);
		BigInteger gcd = b1.gcd(b2);
		return gcd.intValue();
	}

	public static long gcd(long a, long b) {
		BigInteger b1 = BigInteger.valueOf(a);
		BigInteger b2 = BigInteger.valueOf(b);
		BigInteger gcd = b1.gcd(b2);
		return gcd.longValue();
	}
}
