int main(void)
{	
	int sum;
	int sayi;
	printf ("Enter a number: ");
	scanf ("%d",&sayi);
	while ( sayi >= 2 )
	{
	  sum = sayi * (sayi -1 );
		sayi = sayi -2;
	
	}
	 
	printf ("%d\n",sum);
	return 0;

}