res, n = [], int(input())
for i in range(n):
    ope = input().split(' ')
    if ope[0] == 'push':
        res.append(ope[1])
    elif ope[0] == 'size':
        print(len(res))
    elif len(res) != 0 and ope[0] == 'pop':
        res.pop()
    elif len(res) != 0 and ope[0] == 'query':
        print(res[-1])
    else:
        print('Empty')