#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<pair<int, int> > v;
  for (int i = 1; i <= n; i++) {
    int x;
    cin >> x;
    v.push_back(make_pair(x, i));
  }
  sort(v.begin(), v.end());
  if (n == 1) {
    cout << "-1";
    return 0;
  }
  if (n == 2 && v[0].first == v[1].first) {
    cout << "-1";
    return 0;
  }
  cout << "1" << endl;
  cout << v[0].second;
  return 0;
}
