#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define llong long long

int main() {
    int n;
    cin >> n;
    int upper = n / 2;
    int lower = n / 2 + n % 2;

    llong result = (llong)(lower + 1) * upper + lower;
    cout << result << "\n";
}