#include #include using namespace std; using namespace __gnu_pbds; typedef long long ll; typedef unsigned long long ull; typedef long double ld; typedef pair pii; typedef pair pll; typedef pair plli; typedef pair pill; typedef pair, int> piii; const int INF = 0x3f3f3f3f; const ll INFL = 0x3f3f3f3f3f3f3f3fLL; const int MOD = 1e9 + 7; template > using ordered_set = tree; int main() { cin.sync_with_stdio(0); cin.tie(0); int N; cin >> N; cout << N * (N + 1) / 2 << '\n'; return 0; }