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