#include #include #include #include #include #include #include #include #include static const int MOD = 1000000007; using ll = long long; using u32 = unsigned; using u64 = unsigned long long; using namespace std; template constexpr T INF = ::numeric_limits::max()/32*15+208; int main() { int n; cin >> n; cout << (n+1)*(n+2)/2 << "\n"; return 0; }