#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  if (n > 1) {
    if (n == 2 && a[0] == a[1])
      cout << -1 << endl;
    else {
      for (i = 0; i < n - 1; i++) {
        if (a[i] < a[i + 1]) break;
      }
      cout << 1 << endl << i + 1 << endl;
    }
  } else {
    cout << -1 << endl;
  }
  return 0;
}
