#include <bits/stdc++.h>
using namespace std;
int n, i, j, k, rez;
long long a[100005];
void swap(int x, int y) {
  int aux = a[x];
  a[x] = a[y];
  a[y] = aux;
}
bool corect(int x, int y) {
  int ok = 0;
  if (a[x] > a[y])
    ok = 0;
  else
    ok = 1;
  for (int l = 1; l <= n - 1; l++)
    if ((a[l] > a[l + 1] && ok == 1) || (a[l] < a[l + 1] && ok == 0))
      return true;
  return false;
}
int main() {
  scanf("%d", &n);
  for (i = 1; i <= n; i++) scanf("%I64d", &a[i]);
  if (n == 1 || n == 2) {
    printf("-1\n");
    return 0;
  } else {
    for (i = 1; i <= n - 1; i++)
      for (j = i + 1; j <= n; j++) {
        if (a[i] != a[j]) {
          swap(i, j);
          if (corect(i, j)) {
            printf("%d %d\n", i, j);
            return 0;
          } else
            swap(i, j);
        }
        i++;
      }
  }
  printf("-1\n");
  return 0;
}
