#include <iostream>
#include <vector>
#include <functional>
#include <algorithm>
#include <map>
#include <cstdio>
#include <cmath>
#include <iomanip>

using namespace std;

#define rep(i,n) for (int i = 0; i < (n); i++)
#define vi vector<int>
#define vll vector<long long>
#define all(x) x.begin() , x.end()
#define pb push_back()
#define eb emplace_back()


typedef long long ll;
typedef long double ld;

//const int MOD = 1e9 + 7;
//const int MOD = 998244353;
const ll MOD = 1e9 + 7;
//const ll MOD = 998244353;
const ld PI = 3.14159265358979;
const int INF = 1001001001;
const ll LINF = 1001001001001001001;
const int MX = 220000;

ll gcd (ll a , ll b) { if (a < b) swap(a , b); if (a % b == 0) return b; else return gcd(b , a % b); }
ll lcm (ll a , ll b) { return a / gcd(a , b) * b; }
ll lin() { ll x; scanf("%lld" , &x); return x; }
int in() { int x; scanf("%d" , &x); return x; }

void io_setup() {
    cout << fixed << setprecision(20);
}

ll modpow (ll x , ll p) {
    ll ret = 1;
    while (p) {
        if (p % 2 == 1) {
            ret *= x;
            ret %= MOD;
        }
        x *= x;
        x %= MOD;
        p /= 2;
    }
    return ret;
}

ll moddiv (ll a , ll b) {
    return a * modpow(b , MOD - 2) % MOD;
}

ll modsub (ll a , ll b) {
    if (a >= b) return (a - b) % MOD;
    else return (MOD - a + b);
}

vll fact(MX);
vll factinv(MX);
void init_fact () {
    fact[0] = 1;
    for (int i = 1; i < MX; i++) {
        fact[i] = 1LL * i * fact[i - 1] % MOD;
    }
    for (int i = 0; i < MX; i++) {
        factinv[i] = modpow(fact[i] , MOD - 2);
    }
}

ll nCk (ll n , ll k) {
    return ((fact[n] * factinv[k] % MOD) * factinv[n - k] % MOD);
}

bool is_prime (int x) {
    if (x == 2 || x == 3 || x == 5 || x == 7) {
        return true;
    }
    for (ll i = 2; i*i <= x; i++) {
        if (x % i == 0) {
            return false;
        }
    }
    return true;
}

vi prime(MX , 0);
void init_prime() {
    
}

int main() {
    io_setup();
    //init_fact();
    int d = in();
    int l = d / 2;
    int ans = 0;
    for (int i = 1; i <= l; i++) {
        int now = i * (l - i);
        ans = max(ans , now);
    }
    cout << ans << endl;
    return 0;
}