きったんの頭_ん中☆

#! /usr/bin/env python3
"""
pe15.py
https://mind.kittttttan.info/py/pe15
"""

# https://mind.kittttttan.info/py/pe0
from pe import perm, fact

def pe15(m=20, n=20):
    """
    Starting in the top left corner in a 20 by 20 grid,
    how many routes are there to the bottom right corner?
    """
    # return fact(m + n) // (fact(m) * fact(n))
    p = perm(m + n, m)
    f = fact(n)
    print("%d / %d = %d" % (p, f, p // f))

if __name__ == "__main__":
    pe15()