#include <bits/stdc++.h>
using namespace std;
pair<int, int> a[15];
void solve() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i].first, a[i].second = i;
  sort(a + 1, a + 1 + n);
  if (n == 1)
    cout << -1 << endl;
  else if (n == 2 and a[1].first == a[2].first)
    cout << -1 << endl;
  else {
    cout << 1 << endl;
    cout << a[1].second << endl;
  }
}
int main() {
  solve();
  return 0;
}
