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
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Random;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.Reader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyInput in = new MyInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskF solver = new TaskF();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskF {
        public void solve(int testNumber, MyInput in, PrintWriter out) {
            int n = in.nextInt();

            int[][] ab = in.nextIntArray2D(n, 2);

            Random random = new Random();
            int[] values = new int[2 * n];
            for (int i = 0; i < 2 * n; i++) {
                values[i] = ab[i / 2][i % 2];
                swap(values, i, random.nextInt(i + 1));
            }
            Arrays.sort(values);

            for (int[] x : ab) {
                x[0] = Arrays.binarySearch(values, x[0]);
                x[1] = Arrays.binarySearch(values, x[1]);
            }

            UnionFind uf = new UnionFind(values.length);
            int[] cnt = new int[values.length];

            final int inf = values.length;
            int low = -1, high = inf;
            LOOP:
            while (high - low > 1) {
                final int mid = (low + high) / 2;

                for (int i = 0; i <= mid; i++) {
                    uf.data[i] = -1;
                    cnt[i] = 0;
                }
                uf.clear();
                for (int[] x : ab) {
                    int a = x[0];
                    int b = x[1];
                    if (mid < a) {
                        low = mid;
                        continue LOOP;
                    }
                    if (mid >= b) {
                        uf.union(a, b);
                    }
                }

                for (int[] x : ab) {
                    int a = x[0];
                    cnt[uf.root(a)]++;
                }

                for (int i = 0; i <= mid; i++) {
                    if (uf.root(i) == i) {
                        if (uf.size(i) < cnt[i]) {
                            low = mid;
                            continue LOOP;
                        }
                    }
                }
                high = mid;
            }
            out.println(high == inf ? -1 : values[high]);
        }

        static void swap(int[] xs, int i, int j) {
            int t = xs[i];
            xs[i] = xs[j];
            xs[j] = t;
        }

        class UnionFind {
            private int[] data;

            public UnionFind(int size) {
                data = new int[size];
                clear();
            }

            public void clear() {
                Arrays.fill(data, -1);
            }

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

            public void union(int x, int y) {
                if ((x = root(x)) != (y = root(y))) {
                    if (data[y] < data[x]) {
                        final int t = x;
                        x = y;
                        y = t;
                    }
                    data[x] += data[y];
                    data[y] = x;
                }
            }

            public int size(int x) {
                return -data[root(x)];
            }

        }

    }

    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];

        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }

        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }

        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new MyInput.EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }

        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }

        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (MyInput.EndOfFileRuntimeException e) {
            }
            return len;
        }

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

        public int[][] nextIntArray2D(final int n, final int k) {
            final int[][] res = new int[n][];
            for (int i = 0; i < n; i++) {
                res[i] = nextIntArray(k);
            }
            return res;
        }

        static class EndOfFileRuntimeException extends RuntimeException {
        }

    }
}

