#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))
const int MOD = 1000000007;

// aba          1
// ababa        1 + 2         + 1
// abababa      1 + 2 + 3     + 1 + 2
// ababababa    1 + 2 + 3 + 4 + 1 + 2 + 3

int main(){
    ll L;
    cin >> L;
    if(L == 3){
        cout << 1 << endl; return 0;
    }

    ll res = 0;
    ll l = L/2;
    res += l*(l+1)/2;
    res += l*(l-1)/2;
    cout << res << endl;

    return 0;
}