백준-10828번(스택)-python3

import sys
arr=[]
for x in range(int(sys.stdin.readline())):
    a=list(sys.stdin.readline().split())
    if len(a)==2:
        if a[0]=='push':
            arr.append(int(a[1]))
    elif len(a)==1:
        if a[0]=='pop':
            if arr:
                print(arr.pop())
            else:print(-1)
        elif a[0]=='size':
            print(len(arr))
        elif a[0]=='empty':
            if not arr:
                print(1)
            else:
                print(0)
        elif a[0]=='top':
            if arr:
                print(arr[len(arr)-1])
            else:
                print(-1)