#include <bits/stdc++.h>
using namespace std;
int i, j, n, k, res, idx;
int A[100011];
map<int, int> M;
int main() {
  cin >> n;
  int Max = 0;
  for (i = 0; i < n; i++) {
    cin >> A[i];
    M[i]++;
  }
  if (n <= 2) {
    cout << -1 << endl;
    return 0;
  } else {
    for (i = 0; i < n - 1; i++) {
      if (A[i] != A[i + 1]) {
        swap(A[i], A[i + 1]);
        bool u = false, d = false;
        for (j = 0; j < n - 1; j++)
          if (A[j] > A[j + 1]) u = true;
        for (j = 0; j < n - 1; j++)
          if (A[j] < A[j + 1]) d = true;
        if (u && d) {
          cout << i + 1 << " " << i + 2 << endl;
          return 0;
        }
        swap(A[i], A[i + 1]);
      }
    }
  }
  cout << -1 << endl;
  return 0;
}
