#include <stdio.h>

int main() {
    int i = 0;
    int a = 1;
    int sum = 0;
    scanf("%d",&i);
    for(int n=1;n<=i;n++)
    {
       a=(n*(n+1)/2);
       sum +=a;

    }
   printf("%d",sum);
    
    return 0;
}