#include <bits/stdc++.h>

using namespace std;

#define LL long long

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    LL n;
    cin >> n;
    LL ans;
    if (n % 2 == 0) {
        ans = n * n / 4 + n;
    } else {
        ans = (n * n - 1) / 4 + n;
    }

    cout << ans << endl;
    return 0;
}