#include <bits/stdc++.h>
using namespace std;
long long arr[100002];
bool isIncreasing(long long N) {
  for (int i = 1; i < N; i++) {
    if (arr[i] < arr[i - 1]) return false;
  }
  return true;
}
bool isDecreasing(long long N) {
  for (int i = 1; i < N; i++) {
    if (arr[i] > arr[i - 1]) return false;
  }
  return true;
}
int main() {
  long long N, temp;
  cin >> N;
  if (N <= 2) {
    cout << -1 << endl;
    return 0;
  }
  for (int i = 0; i < N; i++) {
    cin >> arr[i];
  }
  if (N == 3) {
    if (arr[0] == arr[2]) {
      cout << -1 << endl;
      return 0;
    }
  }
  for (int i = 1; i < N; i++) {
    if (arr[i] != arr[i - 1]) {
      temp = arr[i];
      arr[i] = arr[i - 1];
      arr[i - 1] = temp;
      if (isIncreasing(N) || isDecreasing(N)) {
        cout << i + 1 << " " << i + 2 << endl;
        return 0;
      }
      cout << i << " " << i + 1 << endl;
      return 0;
    }
  }
  cout << -1 << endl;
  return 0;
}
