#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int mod, t, k = 0, f1, n, i, m, x, j = 0, l, c = 0, r = 0, w, s = 0,
                        d = 0, f = 0, sum = 0, mul, mx1, mx, s1 = 10000000,
                        s2 = 0;
  vector<pair<long long int, pair<long long int, long long int> > > v;
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> l >> r;
    v.push_back({l, {-r, i}});
  }
  sort(v.begin(), v.end());
  for (i = 0; i < n - 1; i++) {
    if (-v[i].second.first >= -v[i + 1].second.first) {
      cout << v[i + 1].second.second << " " << v[i].second.second << endl;
      return 0;
    }
  }
  cout << "-1 -1" << endl;
  return 0;
}
