class Stack:
    def __init__(self):
        self.pole = []

    def push(self, data):
        self.pole += [data]

    def pop(self):
        return self.pole.pop()

    def is_empty(self):
        return self.pole == []

    def size(self):
        return len(self.pole)


def otvor_txt(filename):
    f = open(filename, 'r')
    a = f.readlines()
    f.close()
    return a


a = otvor_txt("HW4.txt")

s = Stack()
print(*a)
test = ""
chyba = bool
j = 0
print()
print()


for i in range(len(a)):
    while j < len(a[i]):
        if a[i][j] == "<":
            while a[i][j] != ">":
                test = ""
                test += str(a[i][j])
                j += 1
                if j == len(a[i]):
                    chyba = True
                    break
            else:
                chyba = True
            if a[i][j-1] != "/":
                s.push(test)
        j += 1
    test = ""

for i in range(s.size()):
    print(s.pop())