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