// // Created by liasa on 28/11/2025. // #include <bits/stdc++.h> using namespace std; #define ll long long #define lp(i, s, e) for (int i = s; i < e; ++i) #define v vector int n, k; int main() { ios_base::sync_with_stdio(0); cin.tie(0); cin >> n >> k; if (n % 2 == 0) { ll ans = ceil((double)n / 2); ans *= n; cout << ans; } else { ll ans =( n / 2) * ceil(n / (double)2); // 1*2 ans +=( n / 2) * ceil(n /(double) 2); cout << ans; } }