#define _CRT_SECURE_NO_WARNINGS #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define aLL(g) (g).begin(),(g).end() #define REP(i, x, n) for(int i = x; i < n; i++) #define rep(i,n) REP(i,0,n) #define F(i,j,k) fill(i[0],i[0]+j*j,k) #define P(p) cout<<(p)< vi; typedef vector vl; typedef vector vd; typedef pair pii; typedef pair pll; typedef long long ll; int dx[] = { 0, 1, 0, -1 }; int dy[] = { -1, 0, 1, 0 }; int sttoi(std::string str) { int ret; std::stringstream ss; ss << str; ss >> ret; return ret; } bool sort_greater(const pair &a, const pair &b) { return a.second > b.second; } int n; double dp[27]; void solve() { int n; cin >> n; ll up, down; ll maxi = -1; for (int i = 0; i <= n; i++){ up = i; down = n - i; maxi = max((up*(down + 1)) + down, maxi); } P(maxi); } int main() { solve(); return 0; }