#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e6 + 20;
vector<int> adj[maxn];
int from[maxn], to[maxn], e, ver;
bool visited[maxn], is[maxn];
void dfs(int v) {
  visited[v] = 1;
  e += adj[v].size();
  ver++;
  for (auto u : adj[v])
    if (!visited[u]) dfs(u);
}
int main() {
  int m;
  scanf("%d", &m);
  vector<int> cmp;
  for (int i = 0; i < m; i++) {
    scanf("%d%d", &from[i], &to[i]);
    cmp.push_back(from[i]);
    cmp.push_back(to[i]);
  }
  sort(cmp.begin(), cmp.end());
  cmp.resize(unique(cmp.begin(), cmp.end()) - cmp.begin());
  int n = cmp.size();
  for (int i = 0; i < m; i++) {
    from[i] = lower_bound(cmp.begin(), cmp.end(), from[i]) - cmp.begin();
    to[i] = lower_bound(cmp.begin(), cmp.end(), to[i]) - cmp.begin();
    adj[to[i]].push_back(from[i]);
    adj[from[i]].push_back(to[i]);
  }
  for (int i = n - 1; i >= 0; i--)
    if (!visited[i]) {
      e = ver = 0;
      dfs(i);
      e /= 2;
      if (e > ver) return cout << -1 << endl, 0;
      if (e == ver - 1) is[i] = 1;
    }
  int tmp = n - 1;
  while (is[tmp]) tmp--;
  cout << cmp[tmp] << endl;
}
