#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  int n;
  cin >> n;
  if (n == 1) {
    cout << -1;
    return 0;
  }
  int a[n];
  int idx[1000] = {-1};
  if (n == 2) {
    cin >> a[0] >> a[1];
    if (a[0] == a[1]) {
      cout << -1;
      return 0;
    } else {
      cout << 1 << endl;
      cout << 1;
      return 0;
    }
  } else
    for (int i = 0; i < n; i++) {
      cin >> a[i];
    }
  int k = (n / 2) + 1;
  cout << k << endl;
  while (k--) {
    int big = 0;
    int bigi = 0;
    for (int i = 0; i < n; i++) {
      if (a[i] != -1) {
        if (a[i] > big) {
          bigi = i + 1;
          big = a[i];
        }
      }
    }
    cout << bigi << " ";
    a[bigi - 1] = -1;
  }
}
