import math
def probability(n,p):
    prob = math.factorial(n) /math.factorial(n-p)  * math.factorial(p)
    return prob


def main():
    n = int(input("Enter the number of lottery balls: "))
    p = int(input("Enter the number of drawn balls: "))
    if n <= 0:
        print("The number of balls must be a positive number.")
    if p > 39:
        print("Ar most the total number of balls can be drawn.")
    else:
        print("The probability of guessing all", n ,"balls correctly is", probability(n,p))
main()