#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> lst(n);
  for (int i = 0; i < n; i++) cin >> lst[i];
  if (n == 1) {
    cout << -1;
    return 0;
  }
  if (n == 2 && lst[0] == lst[1]) {
    cout << -1;
    return 0;
  }
  int mn = 0;
  for (int i = 1; i < n; i++)
    if (lst[mn] > lst[i]) mn = i;
  cout << 1 << '\n' << mn + 1;
  return 0;
}
