题解 | #【模板】队列#

import sys

# for line in sys.stdin:
#   a = line.split()
#    print(int(a[0]) + int(a[1]))


class Myqueue:
    def __init__(self ):
        pass
        self.queue=[]

    def push(self,x):
        self.queue.append(x)

		
		#Pop函数这里出对的时候取对首元素
    def pop(self):
        x =self.queue[0]
        self.queue.remove(x)
        return x



    def front(self):
        x =self.queue[0]
        #self.queue.remove(x)
        return x

opration=[]
n=int(input())



while n > 0:
    s = input()
    opration.append(s)
    n -= 1

queue=Myqueue()
for x in opration:
    if x[0:4] == "push":
        number = int(x[4:])
        queue.push(number)

    elif x == "pop":
        try:
            print(queue.pop())
        except:
            print("error")

    elif x == "front":
        try:
            print(queue.front())
        except:
            print("error")