#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[n];
  int sum1 = 0, sum2 = 0, index = 0, mi = 999999;
  map<int, int> mp;
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
    mp[arr[i]]++;
    if (mi > arr[i]) {
      mi = arr[i];
      index = i;
    }
  }
  if (n == 1 || mp[arr[0]] == 2 && n == 2) {
    cout << -1;
    return 0;
  }
  cout << 1 << endl;
  cout << index + 1;
  return 0;
}
