#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

int main(){

    ll N, M;
    cin >> N;
    M = (N+1)/2;

    cout << M * (M+1) / 2 << endl;

    return 0;
}