import sys
n=int(sys.stdin.readline().strip())
l1=[]
for _ in range(n):
line=list(sys.stdin.readline().strip().split())
cmd=line[0]
if len(line)==2:
num=line[1]
if cmd=='push':
l1.append(num)
elif cmd=='pop':
if len(l1)==0:
print(-1)
else:
k=l1.pop()
print(k)
elif cmd=='top':
if len(l1)==0:
print(-1)
else:
print(l1[-1])
elif cmd=='size':
print(len(l1))
else:
if len(l1)==0:
print(1)
else:
print(0)
코드를 입력하세요