#include <bits/stdc++.h>
using namespace std;
bool ISPRIME(int n) {
  if (n % 2 == 0) return false;
  for (int i = 2; i * i <= n; i++) {
    if (n % i == 0) return false;
  }
  return true;
}
int main() {
  long long unsigned m[110000], n, cnt = 0, cnt1 = 0;
  bool j = false;
  int r;
  int v = 0;
  cin >> n;
  for (int r1 = 0; r1 < n; r1++) cin >> m[r1];
  if (n == 1 || n == 2) {
    cout << -1;
    return 0;
  }
  for (r = 0; r < n - 1; r++) {
    if (m[r] != m[r + 1]) {
      swap(m[r], m[r + 1]);
      j = true;
      for (int r2 = 0; r2 < n - 1; r2++) {
        if (m[r2] <= m[r2 + 1]) {
          cnt++;
          if (cnt >= n - 1) {
            j = false;
            cnt = 0;
            swap(m[r], m[r + 1]);
          }
        }
      }
      for (int r3 = 0; r3 < n - 1; r3++) {
        if (m[r3] >= m[r3 + 1]) {
          cnt1++;
          if (cnt1 >= n - 1) {
            j = false;
            cnt1 = 0;
            swap(m[r], m[r + 1]);
          }
        }
      }
    }
    cnt = cnt1 = 0;
    if (j) {
      cout << r + 1 << ' ' << r + 2;
      return 0;
    }
  }
  cout << -1;
  return 0;
}
