#include <bits/stdc++.h>
using namespace std;
const long long N = 100100, mod = 1e9 + 7, mod2 = 1e9 + 9, mod3 = 998244353,
                sq = 450, base = 727, lg = 30;
long long n, m, x, y, z, w, ans, t, l[N], r[N];
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> l[i] >> r[i];
    if (i == 0) {
      x = l[i];
      y = r[i];
      continue;
    }
    x = min(x, l[i]);
    y = max(y, r[i]);
  }
  for (int i = 0; i < n; i++) {
    if (l[i] == x && r[i] == y) return cout << i + 1, 0;
  }
  cout << -1;
  return 0;
}
