#include <bits/stdc++.h>
using namespace std;
const int N = 2e6 + 10;
int n, u[N], v[N];
int an[N], tot;
int fa[N];
int Find(int x) { return fa[x] ? (fa[x] = Find(fa[x])) : x; }
void Shit() {
  puts("-1");
  exit(0);
}
bool fl[N];
void Hb(int x, int y) {
  x = Find(x);
  y = Find(y);
  if (x == y) {
    if (fl[x]) Shit();
    fl[x] = true;
  } else {
    if (fl[x] && fl[y])
      Shit();
    else if (fl[y])
      fl[x] = true;
    fa[y] = x;
  }
}
int mx[N], mx2[N];
void Update(int x, int y) {
  if (mx[x] < y) {
    mx2[x] = mx[x];
    mx[x] = y;
  } else if (mx2[x] < y)
    mx2[x] = y;
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    scanf("%d%d", u + i, v + i);
    an[++tot] = u[i];
    an[++tot] = v[i];
  }
  sort(an + 1, an + tot + 1);
  tot = unique(an + 1, an + tot + 1) - an - 1;
  for (int i = 1; i <= n; ++i)
    Hb(u[i] = lower_bound(an + 1, an + tot + 1, u[i]) - an,
       v[i] = lower_bound(an + 1, an + tot + 1, v[i]) - an);
  for (int i = 1; i <= tot; ++i) Update(Find(i), an[i]);
  int ans = 0;
  for (int i = 1; i <= tot; ++i) ans = max(ans, fl[Find(i)] ? mx[i] : mx2[i]);
  printf("%d", ans);
  return 0;
}
