#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  long long a[n];
  long long sum = 0;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    sum += a[i];
  }
  if (n == 1) {
    cout << "-1";
  } else if (n == 2) {
    if (a[0] == a[1]) {
      cout << "-1";
    } else {
      cout << 1 << endl;
      cout << 1;
    }
  } else {
    for (int i = 0; i < n; i++) {
      if (a[i] != sum - a[i]) {
        cout << 1 << endl;
        cout << i + 1 << endl;
        return 0;
      }
    }
  }
  return 0;
}
