#include <bits/stdc++.h>
using namespace std;
template <class T1, class T2>
inline void upd1(T1& a, const T2& b) {
  a = a < b ? a : b;
}
template <class T1, class T2>
inline void upd2(T1& a, const T2& b) {
  a = a > b ? a : b;
}
template <class T>
inline bool equ(const T& a, const T& b) {
  return !memcmp(&a, &b, sizeof a);
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
struct ano {
  operator long long() {
    long long x = 0, y = 0, c = getchar();
    while (c < 48) y = c == 45, c = getchar();
    while (c > 47) x = x * 10 + c - 48, c = getchar();
    return y ? -x : x;
  }
} buf;
const int N = 1e6 + 5;
bitset<N * 2> f;
int p[N * 2];
inline int find(int i) { return p[i] == i ? i : p[i] = find(p[i]); }
int a[N], b[N];
int main() {
  int n = buf;
  vector<int> c;
  for (int i = 1; i <= n; ++i) {
    a[i] = buf;
    b[i] = buf;
    c.push_back(a[i]);
    c.push_back(b[i]);
  }
  sort(c.begin(), c.end());
  c.erase(unique(c.begin(), c.end()), c.end());
  for (int i = 1; i <= n; ++i) {
    a[i] = lower_bound(c.begin(), c.end(), a[i]) - c.begin();
    b[i] = lower_bound(c.begin(), c.end(), b[i]) - c.begin();
  }
  int m = c.size() - 1;
  iota(p, p + m + 1, 0);
  for (int i = 1; i <= n; ++i) {
    int u = find(a[i]);
    int v = find(b[i]);
    if (u != v)
      p[u] = v;
    else {
      if (f[u]) return !~puts("-1");
      f[u] = 1;
    }
  }
  for (;; --m) {
    int u = find(m);
    if (f[u]) break;
    f[u] = 1;
  }
  printf("%d\n", c[m]);
}
