#include <bits/stdc++.h>
using namespace std;
int main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, i;
  cin >> n;
  int ar[n];
  for (i = 0; i < n; i++) cin >> ar[i];
  if (n == 1) {
    cout << (-1) << endl;
  } else if (n == 2 and ar[0] == ar[1]) {
    cout << (-1) << endl;
  } else {
    cout << (1) << endl;
    int ans = INT_MAX, cur;
    for (i = 0; i < n; i++) {
      if (ans > ar[i]) {
        ans = ar[i];
        cur = i;
      }
    }
    cout << (cur + 1) << endl;
  }
  return 0;
}
