View Code of Problem 30

#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
int main()
{
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		int k;
		k=(1+n)*n/2;
		printf("%d\n",k);
	}
	return 0;
}