#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  long long t, n, i, j, flag = 0, temp, nodes, a, b, m, k, sz, sm, res;
  long long mn, mx;
  long long l, r;
  long long x, y, z;
  long long c, d;
  t = 1;
  vector<pair<int, int>> v;
  string s;
  char ch;
  while (t--) {
    flag = 0;
    v.clear();
    cin >> n;
    int A = INT_MAX, B = INT_MIN;
    for (i = 0; i < n; i++) {
      cin >> a >> b;
      v.push_back({a, b});
      if (a < A) A = a;
      if (B < b) B = b;
    }
    for (i = 0; i < v.size(); i++) {
      if (v[i].first == A && v[i].second == B) {
        flag = 1;
        break;
      }
    }
    if (flag == 1) {
      cout << i + 1 << endl;
      continue;
    } else {
      cout << "-1";
      continue;
    }
  }
  return 0;
}
