#include <bits/stdc++.h>
using namespace std;
int n, a[100005], b[100005], c[100005];
bool cmp(int x, int y) { return x > y; }
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
  if (n <= 2) {
    puts("-1");
    return 0;
  }
  for (int i = 1; i <= n; ++i) b[i] = c[i] = a[i];
  sort(b + 1, b + 1 + n);
  sort(c + 1, c + 1 + n, cmp);
  for (int i = 1; i < n; ++i) {
    if (a[i] == a[i + 1]) continue;
    swap(a[i], a[i + 1]);
    int j = 1;
    while (j <= n && a[j] == b[j]) {
      j++;
    }
    if (j > n) {
      swap(a[i], a[i + 1]);
      continue;
    }
    j = 1;
    while (j <= n && a[j] == c[j]) {
      j++;
    }
    if (j <= n) {
      printf("%d %d\n", i, i + 1);
      return 0;
    }
    swap(a[i], a[i + 1]);
  }
  puts("-1");
  return 0;
}
