#include <bits/stdc++.h>
using namespace std;
const int N = 2e6 + 10;
const long long mod = 1e9 + 7;
const long long inf = 1e18 + 10;
int a[N], b[N], mark[N], c, E[N];
vector<int> vec, adj[N], cmp[N];
void dfs(int v) {
  mark[v] = 1;
  cmp[c].push_back(v);
  E[c] += (int)(adj[v].size());
  for (int u : adj[v])
    if (!mark[u]) dfs(u);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i] >> b[i];
    vec.push_back(a[i]);
    vec.push_back(b[i]);
  }
  sort((vec).begin(), (vec).end());
  vec.resize(unique((vec).begin(), (vec).end()) - vec.begin());
  for (int i = 1; i <= n; i++) {
    int u = lower_bound((vec).begin(), (vec).end(), a[i]) - vec.begin();
    int v = lower_bound((vec).begin(), (vec).end(), b[i]) - vec.begin();
    adj[u].push_back(v);
    adj[v].push_back(u);
  }
  for (int i = 0; i < (int)(vec.size()); i++) {
    if (mark[i]) continue;
    dfs(i);
    E[c] /= 2;
    c++;
  }
  int ans = 0;
  for (int i = 0; i < c; i++) {
    if ((int)(cmp[i].size()) < E[i]) return cout << -1, 0;
    if ((int)(cmp[i].size()) == E[i]) {
      for (int v : cmp[i]) ans = max(ans, vec[v]);
    } else {
      int mx = 0;
      for (int v : cmp[i]) mx = max(mx, v);
      for (int v : cmp[i])
        if (v != mx) ans = max(ans, vec[v]);
    }
  }
  cout << ans;
  return 0;
}
