#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>


#define INF 0x3f3f3f3f3f3f3f3f

#define ones(x) __builtin_popcountll(x)
#define memss(a, b, sz) memset(arr,b,sz * sizeof (arr[0]))
#define ii pair<ll ,ll >
#define PI ::acos(-1)
#define Eiado ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(0);
typedef long long ll;
typedef long double ld;
#define int  ll
typedef unsigned long long ull;
#define all(v) ((v).begin()),((v).end())
#define rall(v) ((v).rbegin()),((v).rend())
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }

using namespace std;
using namespace __gnu_pbds;
template<typename T>
using orderedset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef pair<long long, long long> pll;
typedef pair<ll, ll> pii;

template<typename T = ll>
istream &operator>>(istream &in, vector<T> &v) {
    for (auto &x: v) in >> x;
    return in;
}

template<typename T = ll>
ostream &operator<<(ostream &out, const vector<T> &v) {
    for (const T &x: v) out << x << ' ';
    return out;
}
/*
 *

 */
///const int N = 5e5 + 5, b = 1e9 + 9, b2 = 31, mod = 1e9 + 7;
const ll inf = 1e18;
const ll M = 998244353;
const ld pi = atan2(0, -1);
const ld eps = 1e-6;
const int mod = 1e9 + 7;
#define x first
#define y second

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


void solve() {
    double n;
    cin >> n;
    cout<<fixed <<setprecision(2)<<n/4;
}


signed main() {
//#ifndef ONLINE_JUDGE
//    freopen("i.txt", "r", stdin);
//    freopen("o.txt", "w", stdout);
//#endif
    Eiado
    // priority_queue<PII, vector<PII>, greater<PII> > pq;
    //pq.emplace(a,make_pair(b,c));
    /*
                 E E E E     0                      D
                 E                                  D
                 E E E E     I    A A A         D D D
                 E           I   A     A       D    D
                 E E E E     I    A A A A       D D D
                                         A

*/
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();


    }


}


/*
 * int pw[N], pw2[N], inv[N], inv2[N], pref[N], pref2[N], prf[N],
        prf2[N];

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

int mul(int a, int b) {
    return 1ll * a * b % mod;
}

int fp(int b, int p) {
    if (p == 0) return 1;
    int ret = fp(b, p >> 1);
    ret = mul(ret, ret);
    if (p & 1) ret = mul(ret, b);
    return ret;
}

void pre() {
    pw[0] = pw2[0] = inv[0] = inv2[0] = 1;
    int mul_inv = fp(b, mod - 2), mul_inv2 = fp(b2, mod - 2);
    for (int i = 1; i < N; i++) {
        pw[i] = mul(pw[i - 1], b);
        pw2[i] = mul(pw2[i - 1], b2);
        inv[i] = mul(inv[i - 1], mul_inv);
        inv2[i] = mul(inv2[i - 1], mul_inv2);
    }
}

pair<int, int> get_hash(int l, int r) {
    int ret = pref[r];
    if (l) ret = (ret - pref[l - 1] + mod) % mod;
    ret = mul(ret, inv[l]);
    int ret2 = pref2[r];
    if (l) ret2 = (ret2 - pref2[l - 1] + mod) % mod;
    ret2 = mul(ret2, inv2[l]);
    return {ret, ret2};
}

pair<int, int> get_hash2(int l, int r) {
    int ret = prf[r];
    if (l) ret = (ret - prf[l - 1] + mod) % mod;
    ret = mul(ret, inv[l]);
    int ret2 = prf2[r];
    if (l) ret2 = (ret2 - prf2[l - 1] + mod) % mod;
    ret2 = mul(ret2, inv2[l]);
    return {ret, ret2};
}

*/