#include <bits/stdc++.h>
using namespace std;
map<string, int> mp;
vector<string> vr;
struct node {
  long long a, b, c;
} w[300050];
long long cmp(struct node a, struct node b) {
  if (a.a == b.a) return a.b < b.b;
  return a.a < b.a;
}
int main() {
  long long a, b, n;
  while (~scanf("%I64d", &n)) {
    for (long long i = 1; i <= n; i++) {
      scanf("%I64d%I64d", &w[i].a, &w[i].b);
      w[i].c = i;
    }
    sort(w + 1, w + n + 1, cmp);
    long long j = w[1].c, f = 0;
    long long maxx = w[1].b;
    for (long long i = 2; i <= n; i++) {
      if (w[i].a == w[i - 1].a) {
        printf("%I64d %I64d\n", w[i - 1].c, w[i].c);
        f = 1;
        break;
      } else {
        if (w[i].b <= maxx) {
          printf("%I64d %I64d\n", w[i].c, j);
          f = 1;
          break;
        }
        if (w[i].b > maxx) {
          maxx = w[i].b;
          j = w[i].c;
        }
      }
    }
    if (!f) printf("-1 -1\n");
  }
  return 0;
}
