#include // #include // #define RANGE_1(e) (boost::irange(0,(e))) // #define RANGE_2(s,e) (boost::irange((s),(e))) // #define RANGE_3(s,e,step) (boost::irange((s), (e), (step))) // #define RANGE_SELECTER(_1,_2,_3,SELECT,...) SELECT // #define range(...) RANGE_SELECTER(__VA_ARGS__, RANGE_3, RANGE_2, RANGE_1) (__VA_ARGS__) #define guard(x) if(x); #define ALL(x) (x).begin(),(x).end() #define RALL(x) (x).rbegin(),(x).rend() #define MAX(x) *max_element(ALL(x)) #define MIN(x) *min_element(ALL(x)) #define BIT(n) (1LL<<(n)) using namespace std; using lint = long long; templateclass range{private:struct I{T x,s;T operator*(){return x;}bool operator!=(I&lhs){if(s<(T)0)return x>lhs.x;return xlint bit(T n){return 1LL<bool amax(T &a,const T &b){if(abool amin(T &a,const T &b){if(a>b){a=b;return 1;}return 0;} struct initialize{initialize(){cin.tie(nullptr);ios::sync_with_stdio(false);};}__ini__; int sum(int x); int main() { int n; cin >> n; cout << sum(n) << endl; } int sum(int x) { if (x == 1) { return 1; } else { return x + sum(x - 1); } }