#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  int arr[n];
  int mn = 100000, idx;
  for (int i = 0; i < n; i++) {
    scanf("%d", &arr[i]);
    if (arr[i] < mn) {
      mn = arr[i];
      idx = i + 1;
    }
  }
  if (n == 1) {
    printf("-1");
    return 0;
  } else if ((n == 2) && (arr[0] == arr[1])) {
    printf("-1");
    return 0;
  }
  printf("1\n");
  printf("%d\n", idx);
  return 0;
}
