#include <bits/stdc++.h>
using namespace std;
int n, a[1000005], r[3], cnt;
bool up, down;
set<int> s;
int main() {
  srand(75435);
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", &a[i]);
  if (n <= 2) {
    cout << -1;
    return 0;
  }
  for (int i = 0; i < n; i++) {
    if (s.find(a[i]) == s.end()) {
      if (cnt < 3) r[cnt++] = i;
      s.insert(a[i]);
    }
  }
  if (cnt == 3) {
    if (r[0] > r[1]) swap(r[0], r[1]);
    if (r[0] > r[2]) swap(r[0], r[2]);
    if (r[1] > r[2]) swap(r[1], r[2]);
    if ((a[r[1]] > a[r[0]] && a[r[1]] > a[r[2]]) ||
        (a[r[1]] < a[r[0]] && a[r[1]] < a[r[2]])) {
      cout << r[0] + 1 << ' ' << r[2] + 1;
      return 0;
    }
    cout << r[0] + 1 << ' ' << r[1] + 1 << endl;
    return 0;
  }
  for (int i = 0; i < n - 1; i++)
    if (a[i] != a[i + 1]) {
      swap(a[i], a[i + 1]);
      up = true;
      down = true;
      for (int j = 0; j < n - 1; j++)
        if (a[j] > a[j + 1])
          up = false;
        else if (a[j] < a[j + 1])
          down = false;
      if (!down && !up) {
        cout << i + 1 << ' ' << i + 2;
        return 0;
      }
      swap(a[i], a[i + 1]);
    }
  cout << -1;
  return 0;
}
