#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  ;
  vector<int> a(n), b, c;
  for (int i = 0; i < n; scanf("%d", &a[i++]))
    ;
  if (n < 3) {
    printf("%d\n", -1);
    ;
    return 0;
  }
  b = a;
  c = a;
  sort(b.begin(), b.end());
  sort(c.rbegin(), c.rend());
  bool ok = 0;
  int ri, rj;
  for (int i = 0; i + 1 < n && !ok; i++) {
    int j = i + 1;
    if (a[j] != a[i]) {
      swap(a[i], a[j]);
      if (a != b && a != c) {
        ok = 1;
        ri = i;
        rj = j;
      }
      swap(a[i], a[j]);
    }
  }
  if (!ok) {
    printf("%d\n", -1);
    ;
  } else
    printf("%d %d\n", ri + 1, rj + 1);
  return 0;
}
