[백준] 10828번 : 스택 with python3

N = int(input())
stack = []

while(N):
    order = input()
    if order[:4] == 'push':
        stack.append(order[4:])
    elif order == 'pop':
        if len(stack) == 0:
            print(-1)
        else:
            print(int(stack.pop()) )

    elif order == 'size':
        print( len(stack))
    elif order == 'empty':
        if len(stack) == 0 :
            print(1)
        else:
            print(0)
    elif order == 'top':
        if len(stack) == 0:
            print(-1)
        else:
            print(int ( stack[len(stack)-1]) )

    N -= 1