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