#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
const int mod = 1e9 + 7;
const int inf = 0x3f3f3f3f;
const long long INF = 0x3f3f3f3f3f3f3f3f;
int a[MAXN];
int main() {
  int n;
  scanf("%d", &n);
  int l = 0, r = 0, maxn = -1, minn = mod, ans1 = -1, ans2 = -1;
  for (int i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
    if (a[i] > maxn) maxn = a[i], r = i;
    if (a[i] < minn) minn = a[i], l = i;
  }
  if (maxn == minn || l == r || n <= 2)
    printf("-1\n");
  else {
    for (int i = 1; i <= n - 2; i++) {
      if (a[i] > a[i + 1] && a[i + 1] > a[i + 2]) {
        ans1 = i;
        ans2 = i + 1;
        break;
      }
      if (a[i] == a[i + 1] && a[i] > a[i + 2]) {
        ans1 = i + 1;
        ans2 = i + 2;
        break;
      }
      if (a[i] > a[i + 1] && a[i + 1] == a[i + 2]) {
        ans1 = i;
        ans2 = i + 1;
        break;
      }
      if (a[i] < a[i + 1] && a[i + 1] < a[i + 2]) {
        ans1 = i;
        ans2 = i + 1;
        break;
      }
      if (a[i] == a[i + 1] && a[i] < a[i + 2]) {
        ans1 = i + 1;
        ans2 = i + 2;
        break;
      }
      if (a[i] < a[i + 1] && a[i + 1] == a[i + 2]) {
        ans1 = i;
        ans2 = i + 1;
        break;
      }
    }
    if (ans1 != -1)
      printf("%d %d\n", ans1, ans2);
    else if (n == 3 && a[1] == a[3])
      printf("-1\n");
    else
      printf("%d %d\n", l, r);
  }
  return 0;
}
