#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const long long mod = 1e9;
const int maxn = 1e6;
const double eps = 1e-7;
struct node {
  int x, y;
  int pos;
} a[(int)3e5 + 100];
bool cmp(node aa, node bb) {
  if (aa.x != bb.x) return aa.x < bb.x;
  return aa.y > bb.y;
}
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d%d", &a[i].x, &a[i].y), a[i].pos = i + 1;
  sort(a, a + n, cmp);
  bool f = false;
  for (int i = 1; i < n; i++) {
    if (a[i - 1].x <= a[i].x && a[i - 1].y >= a[i].y) {
      printf("%d %d", a[i].pos, a[i - 1].pos);
      f = true;
      break;
    }
  }
  if (!f) printf("-1 -1\n");
  return 0;
}
