#include #define rep(i,n) for(int i = 0; i < (n); ++i) #define srep(i,s,t) for (int i = s; i < t; ++i) #define drep(i,n) for(int i = (n)-1; i >= 0; --i) using namespace std; typedef long long int ll; typedef pair P; #define yn {puts("Yes");}else{puts("No");} #define MAX_N 200005 int main() { ll n; cin >> n; ll a = n / 2 + 1; ll b = n / 2; ll ans = a * (a / 1) / 2 + b * (b - 1) / 2; cout << ans << endl; return 0; }