def factorial(number):
    """
    factorial function ex) 4! = 1 * 2 * 3 * 4
    :param number: int
    :return: number!, int
    """
    result = 1
    i = 2
    while i <= number:
        result = result * i
        i = i + 1
    return result


def nCr(n, r):
    """
    combination function
    :param n: total count
    :param r: selected number
    :return: nCr
    """
    denominator = factorial(n-r) * factorial(r)
    numerator = factorial(n)
    return int(numerator / denominator)


help(abs)
help(nCr)
# n = int(input("Input n : "))
# r = int(input("Input r : "))
# #print(nCr(n, r))
# print(f'{n}C{r} = {nCr(n, r)}')


# numbers = input("Input n, r : ").split()
# print(f'{numbers[0]}C{numbers[1]} = {nCr(int(numbers[0]), int(numbers[1]))}')

n, r = input("Input n, r : ").split()
print(f'{n}C{r} = {nCr(int(n), int(r))}')