火车进站

def solve(____):
    from itertools import permutations
    nums = list(map(int, nums.split(____)))
    n = len(____)
    def is_valid(____):
        stack = []
        i = ____
        for num in nums:
            stack.append(____)
            while stack and i < n and stack[-____] == perm[i]:
                stack.pop()
                i += ____
        return i == n
    valid = []
    for perm in permutations(____):
        if is_valid(____):
            valid.append('____'.join(map(____)))
    for v in sorted(____):
        print(____)