#include <bits/stdc++.h>
using namespace std;
const int N = (int)(3e4) + 1, M = 501;
int main() {
  ios::sync_with_stdio(0);
  ios_base::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);
  int n, s = 0, x;
  bool b = 1;
  cin >> n;
  if (n == 1) return cout << -1 << endl, 0;
  int arr[n];
  for (int i = 0; i < n; i++) cin >> arr[i], s += arr[i];
  for (int i = 0; i < n; i++)
    if (s - arr[i] != arr[i]) return cout << 1 << endl << i + 1 << endl, 0;
  cout << -1 << endl;
  return 0;
}
