MOD = 10 ** 9 + 7

class Solution:
    def countOrders(self, n: int) -> int:
        # Answer is (2n)! / 2^n
        # as we can consider all the distinct shufflings of the array [1, 1, 2, 2, ..., n, n]
        # The first occurrence of a number is it's pickup, the second is it's drop-off

        # Calculating this number modulu MOD, is annoying, but we can simplify this into
        # n! * (1 * 3 * ... * (2n - 1)) % MOD

        return functools.reduce(
            lambda a, b: (a * b) % MOD,
            itertools.chain(range(1, n + 1), range(1, 2 * n, 2)),
        )