#include<bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    ll n;
    cin>>n;
    n = (n+1) / 2;
    ll ans = n * (n+1) / 2;
    cout<<ans<<endl;
}