#include <bits/stdc++.h>
using namespace std;
long a[1000000], m, n, i, j, k, l, ma, mi;
int main() {
  cin >> n;
  for (i = 1; i <= n; i++) cin >> a[i];
  if (n <= 2) {
    cout << -1 << endl;
    return 0;
  }
  for (i = 1; i <= n - 2; i++)
    if (a[i] != a[i + 2]) {
      if (a[i] == a[i + 1]) {
        cout << i + 1 << " " << i + 2 << endl;
        return 0;
      } else if (a[i + 1] == a[i + 2]) {
        cout << i << " " << i + 1 << endl;
        return 0;
      } else {
        if (a[i] > a[i + 1] && a[i] > a[i + 2])
          ma = i;
        else if (a[i + 1] > a[i] && a[i + 1] > a[i + 2])
          ma = i + 1;
        else
          ma = i + 2;
        if (a[i] < a[i + 1] && a[i] < a[i + 2])
          mi = i;
        else if (a[i + 1] < a[i] && a[i + 1] < a[i + 2])
          mi = i + 1;
        else
          mi = i + 2;
        if (ma != i + 1) {
          if (ma != i + 2)
            cout << i << " " << i + 1 << endl;
          else
            cout << i + 2 << " " << i + 1 << endl;
          return 0;
        }
        if (mi != i + 1) {
          if (mi != i + 2)
            cout << i << " " << i + 1 << endl;
          else
            cout << i + 2 << " " << i + 1 << endl;
          return 0;
        }
      }
    }
  if (n == 3 && a[1] == a[3]) {
    cout << -1 << endl;
    return 0;
  } else if (a[1] != a[2])
    cout << 1 << " " << 2 << endl;
  else
    cout << -1 << endl;
}
