#include <bits/stdc++.h>
using namespace std;
int n, v[20], sum;
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> v[i];
    sum += v[i];
  }
  if (n == 1) {
    cout << "-1";
    return 0;
  }
  if (n == 2) {
    if (v[1] == v[2]) {
      cout << "-1";
      return 0;
    } else {
      cout << "1\n1";
      return 0;
    }
  }
  if (v[1] == sum - v[1])
    cout << "1\n2";
  else
    cout << "1\n1";
  return 0;
}
