#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 2;
bitset<2 * maxn> mark;
int V[2 * maxn], a[maxn], b[maxn], E[2 * maxn], C[2 * maxn];
vector<int> compress, adj[2 * maxn];
map<int, int> M;
void dfs(int v, int c) {
  mark[v] = 1;
  C[v] = c;
  V[v]++;
  for (auto u : adj[v]) {
    E[v]++;
    if (!mark[u]) {
      dfs(u, c);
      E[v] += E[u];
      V[v] += V[u];
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int m;
  cin >> m;
  for (int i = 0; i < m; i++) {
    cin >> a[i] >> b[i];
    compress.push_back(a[i]);
    compress.push_back(b[i]);
  }
  sort(compress.begin(), compress.end());
  compress.resize(unique(compress.begin(), compress.end()) - compress.begin());
  int sz = compress.size();
  for (int i = 0; i < sz; i++) {
    M[compress[i]] = i;
  }
  for (int i = 0; i < m; i++) {
    a[i] = M[a[i]];
    b[i] = M[b[i]];
    adj[a[i]].push_back(b[i]);
    adj[b[i]].push_back(a[i]);
  }
  for (int i = 0; i < sz; i++) {
    if (mark[i]) continue;
    dfs(i, i);
    E[i] = E[i] / 2;
    if (E[i] > V[i]) {
      cout << -1;
      return 0;
    }
  }
  mark = 0;
  int i = sz - 1;
  for (; i; i--) {
    if (V[C[i]] == E[C[i]]) break;
    if (mark[C[i]]) break;
    mark[C[i]] = 1;
  }
  cout << compress[i];
}
