#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[n + 5];
  int minn = INT_MAX;
  int ind;
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
    if (arr[i] < minn) {
      minn = arr[i];
      ind = i + 1;
    }
  }
  sort(arr, arr + n);
  if (n == 1) {
    cout << -1 << endl;
  } else if (n == 2 && (arr[0] == arr[1])) {
    cout << -1 << endl;
  } else {
    cout << 1 << endl;
    cout << ind << endl;
  }
  return 0;
}
