题解 | #【模板】队列#

# import sys

# for line in sys.stdin:
#     a = line.split()
#     print(int(a[0]) + int(a[1]))
class Queue:
    def __init__(self) -> None:
        self.queue = []
    def push(self,x):
        self.queue.append(x)
    def pop(self):
        if len(self.queue) != 0:
            print(self.queue.pop(0))
        else:
            print('error')
    def front(self):
        if len(self.queue) != 0:
            print(self.queue[0])
        else:
            print('error')

    def see(self,n):
        for j in range(n):
            a = [i for i in input().split()]
            if len(a) == 2:
                b = int(a[1])
                self.push(b)
            else:
                if a[0] == 'pop':
                    self.pop()
                else:
                    self.front()

n = int(input())
queue = Queue()
queue.see(n)