'''
Starting in the top left corner of a 2×2 grid, and only being able to move to the right and down, there are exactly 6 routes to the bottom right corner.

How many such routes are there through a 20×20 grid?
'''
import math

n = 20

result = (math.factorial(2 * n))/(math.factorial(n)**2) # See central binomial coefficients (https://en.wikipedia.org/wiki/Central_binomial_coefficient)

print(int(result))
