#include <bits/stdc++.h>

#define all(x) (x).begin(), (x).end()
#define endl '\n'
#define yes cout << "YES\n";
#define no cout << "NO\n";
#define fr(n) for(ll i = 0 ; i < n ; i++)
#define frj(n) for(ll j = 0 ; j < n ; j++)
#define ll long long
#define files    freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
#define Ksakkary ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

const ll mod = 1e9 + 7;

using namespace std;


ll gcd(ll a, ll b) {
    if (b == 0) return a;
    return gcd(b, a % b);
}

ll mult(ll a, ll b) {
    return ((a % mod) * (b % mod)) % mod;
}

ll add(ll a, ll b) {
    return ((a % mod) + (b % mod)) % mod;
}

ll subtract(ll a, ll b) {
    return ((a % mod) - (b % mod) + (2 * mod)) % mod;
}

const unsigned ll N = 2e6 + 5;

int knightX[] = {-2, -2, 2, 2, 1, 1, -1, -1};
int knighty[] = {-1, 1, -1, 1, -2, 2, -2, 2};

int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, -1, 0, 1, -1, 1, -1, 1};
char di[] = {'D', 'L', 'U', 'R'};


void solve() {
    double n ; cin >> n;
    cout << n/4;
}

int main() {
    Ksakkary
#ifndef ONLINE_JUDGE
    files
#endif
    // sieve();
    ll t = 1;
//    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}