search_trees

class Node:
    def __init__(self, value, left=None, right=None):
        self.value = value
        self.right = right
        self.left = left


def get_combs(n, comb, res, visited):
    if len(comb) == n:
        tree = get_tree(comb)
        if check_node(tree):
            comb = tree_to_comb(tree)
            res.add(tuple(comb))
    else:
        for i in range(n):
            if not visited[i]:
                comb.append(i)
                visited[i] = True
                get_combs(n, comb, res, visited)
                comb.pop()
                visited[i] = False
        return res


def check_node(node, lo=-1, hi=1000):
    if not lo < node.value < hi:
        return False
    if node.left and check_node(node.left, lo=lo, hi=node.value) is False or \
            node.right and check_node(node.right, lo=node.value, hi=hi) is False:
        return False
    return True


def get_tree(comb):
    root = Node(comb[0])
    for i in range(1, len(comb)):
        num = comb[i]
        node = root
        while True:
            if num < node.value:
                if node.left:
                    node = node.left
                else:
                    node.left = Node(num)
                    break
            if num > node.value:
                if node.right:
                    node = node.right
                else:
                    node.right = Node(num)
                    break
    return root


def tree_to_comb(root):
    nodes = [root]
    comb = []
    while nodes:
        next_nodes = []
        for node in nodes:
            comb.append(node.value)
            if node.left:
                next_nodes.append(node.left)
            if node.right:
                next_nodes.append(node.right)
        nodes = next_nodes
    return comb


def count_trees(n):
    combs_set = get_combs(n, comb=[], res=set(), visited=[False] * n)
    result = len(combs_set)
    return result


n = int(input())
print(count_trees(n))