#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>

#define rep(i,x) for(i=0;i<x;i++)
#define rrep(i,x) for(i=x-1;i>=0;i--)
#define rep_to(a,i,x) for(i=a;i<x;i++)
#define si_1(x) scanf("%d",&x)
#define si_2(x,y) scanf("%d %d",&x,&y)
#define debug(x) printf("x:%d\n",x)

int main()
{
	int i,j,k,num[10]={},n;
	int sum=2;
	double count=1,plus;
	while(si_1(n)!=EOF)
	{/*
		count=0;
		rep(i,1000)
		{
			num[0]=n-i;
			rep(j,num[0]+1)
			{
				num[1]=n-(i+j);
				rep(k,num[1]+1)
				{
					num[2]=n-(i+j+k);
					if(num[2]<=1000 && num[2]>=0)count++;
					printf("%d+%d+%d+%d=%d\n",i,j,k,num[2],n);
				}
				if(n<=(i+j))break;
			}
			if(n<=i)break;
		}
	*/
		sum=2;
		count=1;
		plus=1;
		rep(i,n)
		{
			plus+=sum;
			count+=plus;
			sum++;
		}
		printf("%.0f\n",count);
	}

	
	return 0;
}