def main(a=20,b=20): return factorial(a+b)/(factorial(a)*factorial(b)) print main()
def main(n = 100): return reduce(lambda k,y: int(k)+int(y), str(factorial(n)),0) print main()
def paths(x, y): return factorial(x + y) // (factorial(x) * factorial(x + y - x))
from useful import factorial print(sum(map(int, str(factorial(100)))))