78007

Run ID	Author	Problem	Lang	Verdict	Time	Memory	Code Length	Submit Time
78007	sh25_wangtaojie	求和	C++	Accepted	0 MS	244 KB	129	2025-12-26 15:15:42

// #include<bits/stdc++.h> using namespace std; int n; int main(){ cin>>n; cout<<n*(n+1)/2<<endl; return 0; }