#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, d, res = 0, k, lo = 10000, no = 0, loi;
  int arr[109];
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
    if (arr[i] < lo) {
      no = 0;
      lo = arr[i];
      loi = i;
    } else if (arr[i] == lo)
      no++;
  }
  if (n == 2 && arr[0] != arr[1])
    res = 1, k = 1;
  else if (n > 2 && no != n)
    res = 1, k = loi;
  else if (n > 2 && n % 2 == 1)
    res = 1, k = loi;
  if (res)
    cout << "1\n" << k + 1;
  else
    cout << "-1";
  return 0;
}
