#include <bits/stdc++.h>
using namespace std;
int n;
int main() {
  ios::sync_with_stdio(false);
  cin >> n;
  if (n == 1)
    cout << -1;
  else {
    pair<int, int> a[1000];
    for (int i = 0; i < n; ++i) {
      cin >> a[i].first;
      a[i].second = i;
    }
    sort(a, a + n);
    if (n == 2 && a[0].first == a[1].first)
      cout << -1;
    else {
      cout << 1 << endl << a[0].second + 1;
    }
  }
  return 0;
}
