View Code of Problem 30

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<vector>
#include<map>
#include<string>
#include<set>
using namespace std;
int main(){
    int n;
    while(~scanf("%d",&n))
    {
        cout<<(n+1)*n/2<<endl;
    }
    return 0;
}