n = int(input())
def jiechen(n):
    res = 1
    for i in range(1, n+1):
        res *= i
    return res
n1 = jiechen(n)
n2 = jiechen(2*n-n)
n3 = jiechen(2*n)
print(int((n3/(n1*n2))/(n+1)))

n个节点可以构成 1/n+1(Cn 2n)棵树