#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
enum { MOD0 = 1000000000, MOD7 = 1000000007, MOD9 = 1000000009 };
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int n;
  cin >> n;
  int a[10];
  int sum = 0;
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
    sum += a[i];
  }
  if (n == 1) {
    cout << -1 << '\n';
    return 0;
  } else if (n == 2 && a[0] == a[1]) {
    cout << -1 << '\n';
    return 0;
  }
  if (sum & 1) {
    cout << 1 << '\n' << 1 << '\n';
    return 0;
  }
  if (a[0] == sum / 2) {
    cout << 2 << '\n';
    cout << "1 2" << '\n';
  } else {
    cout << 1 << '\n';
    cout << 1 << '\n';
  }
  return 0;
}
