#include<algorithm>
#include<iostream>
#include<vector>
#include<string>
#include<random>
#include<cmath>
#include<stack>
#include<map>
#include <iomanip>
#include <queue>
#include <set>
using namespace std;
using ll = long long;
using ull = unsigned long long;
ll mod = 1e9 + 7;
ll pv(ll a, ll b) {
if (b == 0)return 1;
ll res = (pv(a, b / 2));
if (b % 2) {
return (((res * res) % mod) * (a % mod)) % mod;
}
else {
return (res * res) % mod;
}
}
ll gcd(ll n1, ll n2)
{
if (n2 != 0)
return gcd(n2, n1 % n2);
else
return n1;
}
void solve() {
ll n, k; cin >> n >> k;
if (n % 2 == 0) {
cout << (n / 2) * n << endl;;
}
else {
ll cnt = (n + 1) / 2;
cout << cnt * (n / 2) + (n - cnt) * cnt << endl;
}
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cin.tie(nullptr);
ll _ = 1;
//cin >> _;
while (_--)
{
solve();
}
}
