#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
bool sortcol(const vector<int>& v1, const vector<int>& v2) {
  return v1[0] < v2[0];
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  vector<vector<int> > arr(n, vector<int>(2));
  for (int i = 0; i < n; i++) {
    cin >> arr[i][0];
    arr[i][1] = i;
  }
  sort(arr.begin(), arr.end(), sortcol);
  if (n == 1) {
    cout << -1;
    exit(0);
  }
  if (n == 2) {
    if (arr[0][0] == arr[1][0]) {
      cout << -1;
      exit(0);
    }
  }
  cout << 1 << endl;
  cout << arr[0][1] + 1;
  return 0;
}
