#include <cstdio>
#include <iostream>

using namespace std ;

long long int dots = 0 ;
long long int n, komb, gaus ;

int main ( void ) {
    scanf ( "%lld", &n ) ;

    dots = ( ( ( n * ( n + 1 ) ) / 2 ) * 2 ) + n ;
    gaus = ( n * ( n + 1 ) ) / 2 ;
    for ( int i = 2 ; i <= n ; ++i ) {
        komb = n - i + 1 ;
        dots += i * komb ;
        dots += gaus - ( ( ( i - 1 ) * i ) / 2 ) ;
    }

    printf ( "%lld\n", dots ) ;

    return 0 ;
}