#!/usr/bin/python3
# A Queue (first-in first-out)
#

# fixed-size array implementation
Q = [None]*100
# meta-data
# ...

def enqueue(x):
    global Q
    # ...

def dequeue():
    global Q
    # ...

def is_empty():
    global Q
    # ...

import sys

for l in sys.stdin:             # line-by-line iteration
    l = l.split()
    if len(l) == 0:             # skip empty lines
        continue
    if l[0] == 'enqueue':
        enqueue(l[1])
    elif l[0] == 'dequeue':
        print(dequeue())
    elif l[0] == 'is_empty':
        print(is_empty())
    elif l[0] == '?':
        print('Q =', Q)
    else:
        print('unknown command', l[0])