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
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