#include <iostream>
#include <vector>

using namespace std;

int main() {
    int l;
    cin >> l;
    int count{};
    vector<int> v;
    for (int i = 2; i <= l; ++i) {
        if (i % 2 == 1) v.push_back(i);
    }
    for (auto elem : v) {
        count += (l - elem +1);
    }
    cout << count << endl;
    return 0;
}