// // 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; ll ans = ceil(n/2); ans*=n; cout<<ans; }