n = int(input()) li = [] for i in range(n): inp = input() if ' ' in inp: a, b = inp.split() else: a = inp

print(a, b)

if a == 'push':
    li.append(int(b))
else:

print('!!!!!!', li)

    if len(li) == 0:
        print('error')
    else:
        if a == 'pop':
            print(li.pop(-1))
        elif a == 'top':
            print(li[-1])