View Code of Problem 30

#include<stdio.h>
#include<string.h>
#include<math.h>
int main()
{
	int n;
	long long sum = 0;
	while(scanf("%d",&n) != EOF)
	{
		sum = 0;
		for(int i = 1;i<= n;i++)
		{
			sum = sum+i;
		}
		printf("%lld\n",sum);
	}
	return 0;
}