#include <bits/stdc++.h>
using namespace std;
void swap(int &a, int &b) {
  int temp = a;
  a = b;
  b = temp;
}
int main() {
  int n;
  cin >> n;
  int x[n], y[n], min_x = INT_MAX, max_y = INT_MIN;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
    if (x[i] < min_x) min_x = x[i];
    if (y[i] > max_y) max_y = y[i];
  }
  int k = 0, res = -1;
  while (k < n) {
    if (x[k] == min_x) {
      if (y[k] == max_y) {
        res = k + 1;
        break;
      }
    }
    k++;
  }
  cout << res << endl;
}
