package DSinn;

public class PRB
{
    public static long factorial (int n)
    {
	if (n > 1)
	{
	    for (int i = n - 1 ; i > 1 ; i--)
		n *= i;
	    return n;
	}
	else if (n < 0)
	    return -1;
	else
	    return 1;
    }


    public static long nPr (int n, int r)
    {
	if (n < r)
	    return -1;
	else
	    return factorial (n) / factorial (n - r);
    }


    public static long nCr (int n, int r)
    {
	if (n < r)
	    return -1;
	else
	    return nPr (n, r) / factorial (r);
    }
}