#include <stdio.h>

int main() 
{
    int n = 0;
    scanf("%d",&n);
    int i = 0;
    int num = 0;
    int sum = 0;
    for(i=1;i<=n;i++)
    {
        num += i;
        sum += num; 
    }
    printf("%d",sum);
    return 0;
}