View Code of Problem 30

#include<iostream>
#include<vector>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<string>
using namespace std;

int main()
{
	
	long long int n;
	while (cin >> n)
	{
		long long sum=0;
		for (int i = 1;i <= n;i++)
			sum += i;
		printf("%lld\n", sum);
	}
}