#include <bits/stdc++.h>
using namespace std;
map<long long int, long long int> mp;
int main() {
  int n, c = 0, x = 0, a[200], i, j;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> a[i];
    c += a[i];
  }
  if (n == 1) x = 1;
  if (n == 2 && a[0] == a[1]) x = 1;
  if (x == 1)
    cout << -1;
  else {
    cout << 1 << endl;
    for (i = 0; i < n; i++) {
      if (2 * a[i] != c) {
        cout << i + 1;
        break;
      }
    }
  }
  return 0;
}
