Contest1258/D.cpp

#include<iostream>

using namespace std;

int main(int argc, char const *argv[]) {
    for (int n; cin >> n;) {
        if (n == 1)
            cout << 1 << endl;
        else if (n < 4 || n % 4 != 0)
            cout << -1 << endl;
        else
            cout << (n / 4) + 1 << endl;
    }
    return 0;
}