#include <bits/stdc++.h>
using namespace std;
const int INF = 987654321;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<pair<int, int>> arr(n);
  for (int i = 0; i < (n); ++i) {
    cin >> arr[i].first;
    arr[i].second = i;
  }
  sort(arr.begin(), arr.end());
  if (arr.size() == 1)
    cout << -1;
  else if (arr.size() == 2) {
    if (arr[0].first == arr[1].first)
      cout << -1;
    else {
      cout << 1 << '\n';
      cout << arr[0].second + 1;
    }
  } else {
    cout << 1 << '\n';
    cout << arr[0].second + 1;
  }
  return 0;
}
