#include <bits/stdc++.h>
using namespace std;
int dx[4] = {-1, 1, 0, 0}, dy[4] = {0, 0, -1, 1};
char dc[4] = {'N', 'S', 'W', 'E'};
vector<pair<int, int> > v;
int main() {
  int n, a[1000005];
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    v.push_back(make_pair(a[i], i));
  }
  sort(v.begin(), v.end());
  if ((n == 2 && a[1] == a[2]) || (n == 1))
    cout << "-1\n";
  else {
    cout << "1\n" << v[0].second << endl;
  }
}
