#include #include #include using namespace std; #define RREP(i,s,e) for (i = e-1; i >= s; i--) #define rrep(i,n) RREP(i,0,n) #define REP(i,s,e) for (i = s; i < e; i++) #define rep(i,n) REP(i,0,n) #define INF 1e8 typedef long long ll; int main() { ll n, u, l; cin >> n; l = n / 2; u = n - n / 2; cout << l * u + l + u << endl; return 0; }