Polycarp studies in Berland State University. Soon he will have to take his exam. He has to pass exactly n exams.

For the each exam i there are known two days: a_i — day of the first opportunity to pass the exam, b_i — day of the second opportunity to pass the exam (a_i < b_i). Polycarp can pass at most one exam during each day. For each exam Polycarp chooses by himself which day he will pass this exam. He has to pass all the n exams.

Polycarp wants to pass all the exams as soon as possible. Print the minimum index of day by which Polycarp can pass all the n exams, or print -1 if he cannot pass all the exams at all.

Input

The first line of the input contains one integer n (1 ≤ n ≤ 10^6) — the number of exams.

The next n lines contain two integers each: a_i and b_i (1 ≤ a_i < b_i ≤ 10^9), where a_i is the number of day of the first passing the i-th exam and b_i is the number of day of the second passing the i-th exam.

Output

If Polycarp cannot pass all the n exams, print -1. Otherwise print the minimum index of day by which Polycarp can do that.

Examples

Input

2
1 5
1 7


Output

5


Input

3
5 13
1 5
1 7


Output

7


Input

3
10 40
40 80
10 80


Output

80


Input

3
99 100
99 100
99 100


Output

-1
/**
 * Created by Baelish on 8/28/2018.
 */

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

public class F_DSU {
    public static void main(String[] args)throws Exception {
        FastReader in = new FastReader(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        n = in.nextInt();
        int brr[] = new int[2*n];
        for (int i = 0; i < 2*n; i+= 2) {
            brr[i] = in.nextInt();
            brr[i+1] = in.nextInt();
        }

        arr = shrink(brr);
        int imap[] = new int[2*n];
        for (int i = 0; i < 2*n; i++) {
            imap[arr[i]] = brr[i];
        }

        int idx = binarySearch(arr.length);
        if(idx >= arr.length) pw.println(-1);
        else pw.println(imap[idx]);

        pw.close();
    }
    static int n, arr[];

    static int binarySearch(int H) {
        int lo = 0, hi = H, mid;
        while (lo < hi) {
            mid = (lo + hi) / 2;
            if (check(mid)) hi = mid;
            else lo = mid + 1;
        }
        if(lo > 0 && check(lo-1)) return lo-1;
        return lo;
    }

    static boolean check(int m){
        DJSet dsu = new DJSet(2*n);
        for (int i = 0; i < n; i++) {
            int u = arr[2*i], v = arr[2*i+1];
            if(u > m) return false;
            if(v > m){
                if(++dsu.cycle[dsu.root(u)] >= 2) return false;
            }
            else{
                if(!dsu.union(u, v)){
                    if(++dsu.cycle[dsu.root(u)] >= 2) return false;
                }
                else{
                    if(dsu.cycle[dsu.root(u)] >= 2) return false;
                }
            }
        }
        return true;
    }

    public static class DJSet {
		public int[] upper;
		public int[] cycle;

		public DJSet(int n) {
			upper = new int[n];
			Arrays.fill(upper, -1);
			cycle = new int[n];
		}

		public int root(int x) {
			return upper[x] < 0 ? x : (upper[x] = root(upper[x]));
		}

		public boolean equiv(int x, int y) {
			return root(x) == root(y);
		}

		public boolean union(int x, int y) {
			x = root(x);
			y = root(y);
			if (x != y) {
				if (upper[y] < upper[x]) {
					int d = x;
					x = y;
					y = d;
				}
				upper[x] += upper[y];
				upper[y] = x;
				
				cycle[x] += cycle[y];
			}
			return x != y;
		}

		public int count() {
			int ct = 0;
			for (int u : upper)
				if (u < 0)
					ct++;
			return ct;
		}
	}

	
	public static int[] shrinkX(int[] a) {
		int n = a.length;
		long[] b = new long[n];
		for (int i = 0; i < n; i++)
			b[i] = (long) a[i] << 32 | i;
		Arrays.sort(b);
		int[] ret = new int[n];
		int p = 0;
		ret[0] = (int) (b[0] >> 32);
		for (int i = 0; i < n; i++) {
			if (i > 0 && (b[i] ^ b[i - 1]) >> 32 != 0) {
				p++;
				ret[p] = (int) (b[i] >> 32);
			}
			a[(int) b[i]] = p;
		}
		return Arrays.copyOf(ret, p + 1);
	}

    public static int[] shrink(int[] a) {
        int n = a.length;
        long[] b = new long[n];
        for(int i = 0;i < n;i++)b[i] = (long)a[i]<<32|i;
        Arrays.sort(b);
        int[] ret = new int[n];
        int p = 0;
        for(int i = 0;i < n;i++) {
            if(i>0 && (b[i]^b[i-1])>>32!=0)p++;
            ret[(int)b[i]] = p;
        }
        return ret;
    }

    static void debug(Object...obj) {
        System.err.println(Arrays.deepToString(obj));
    }

    static class FastReader {
        InputStream is;
        private byte[] inbuf = new byte[1024];
        private int lenbuf = 0, ptrbuf = 0;
        static final int ints[] = new int[128];

        public FastReader(InputStream is){
            for(int i='0';i<='9';i++) ints[i]=i-'0';
            this.is = is;
        }

        public int readByte(){
            if(lenbuf == -1)throw new InputMismatchException();
            if(ptrbuf >= lenbuf){
                ptrbuf = 0;
                try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
                if(lenbuf <= 0)return -1;
            }
            return inbuf[ptrbuf++];
        }

        public boolean isSpaceChar(int c) {
            return !(c >= 33 && c <= 126);
        }
        public int skip() {
            int b;
            while((b = readByte()) != -1 && isSpaceChar(b));
            return b;
        }

        public String next(){
            int b = skip();
            StringBuilder sb = new StringBuilder();
            while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public int nextInt(){
            int num = 0, b;
            boolean minus = false;
            while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
            if(b == '-'){
                minus = true;
                b = readByte();
            }

            while(true){
                if(b >= '0' && b <= '9'){
                    num = (num<<3) + (num<<1) + ints[b];
                }else{
                    return minus ? -num : num;
                }
                b = readByte();
            }
        }

        public long nextLong() {
            long num = 0;
            int b;
            boolean minus = false;
            while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
            if(b == '-'){
                minus = true;
                b = readByte();
            }

            while(true){
                if(b >= '0' && b <= '9'){
                    num = (num<<3) + (num<<1) + ints[b];
                }else{
                    return minus ? -num : num;
                }
                b = readByte();
            }
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
       /* public char nextChar() {
            return (char)skip();
        }*/

        public char[] next(int n){
            char[] buf = new char[n];
            int b = skip(), p = 0;
            while(p < n && !(isSpaceChar(b))){
                buf[p++] = (char)b;
                b = readByte();
            }
            return n == p ? buf : Arrays.copyOf(buf, p);
        }

        /*private char buff[] = new char[1005];
        public char[] nextCharArray(){
            int b = skip(), p = 0;
            while(!(isSpaceChar(b))){
                buff[p++] = (char)b;
                b = readByte();
            }
            return Arrays.copyOf(buff, p);
        }*/
    }
}