// Arup Guha
// 6/21/2023
// Solution to SIUCF CP Final Contest Problem: Metronome
// https://open.kattis.com/problems/metronome

using namespace std;
#include <bits/stdc++.h>

int main() {
    int n;
    cin >> n;

    // Either read in by double or divide by double.
    cout << n/4.0 << endl;
    return 0;
}