C :

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

C++ :

 #include <stdio.h>
 int main()
 {
    long long n;
    while(~scanf("%lld",&n)&&n){
        printf("%lld\n",(n+1)*n/2+1);
    }
    return 0;
 }

Java :

import java.util.Scanner;


public class Main {

	
	public static int f(int n)
	{
		if(n==1)
		{
			return 2;
		}else
		{
			return n+f(n-1);
		}
	}

	public static void main(String[] args) {
		
		Scanner scan=new Scanner(System.in);
		while(scan.hasNext())
		{
			int n=scan.nextInt();
			int sum=0;
			if(n!=0)
			{
				sum=f(n);
				System.out.println(sum);
			}
			
		}
		

	}

}