1006 Sum Problem

别做。。。浪费生命......

#include<iostream>#include<cstdio>#include<cmath>#include<vector>#include<algorithm>#include<queue>#include<ctime>#include<cstring>#include<stdlib.h>#include<map>using namespace std;double x;int main(){while(cin>>x)cout<<(x+1)*x/2<<endl;return 0;}