#include <bits/stdc++.h>
using namespace std;
void sober() {
  long long int n, x = 0, a = 0, b = 0, y = 0, sum = 0, k = 0, m = 0;
  cin >> n;
  set<long long int> sett;
  map<long long int, long long int> mp;
  vector<long long int> v(n);
  for (long long int i = 0; i < n; i++)
    cin >> v[i], sett.insert(v[i]), mp[v[i]] = i;
  if ((sett.size() == 1 and n == 2) or n == 1) {
    cout << "-1\n";
    return;
  }
  cout << 1 << '\n';
  cout << mp[*min_element(begin(v), end(v))] + 1;
  return;
}
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t = 1;
  while (t--) {
    sober();
  }
}
