Baek10866_2.py

import collections
import sys

n = int(sys.stdin.readline())
deq = collections.deque([])
for i in range(n):
    a = list(sys.stdin.readline().split())

    if a[0] == "push_front":
        deq.appendleft(a[1])
    elif a[0] == "push_back":
        deq.append(a[1])
    elif a[0] == "pop_front":
        if len(deq) == 0:
            print(-1)
        else:
            print(deq.popleft())
    elif a[0] == "pop_back":
        if len(deq) == 0:
            print(-1)
        else:
            print(deq.pop())
    elif a[0] == "size":
        print(len(deq))
    elif a[0] == "empty":
        if len(deq) == 0:
            print(1)
        else:
            print(0)
    elif a[0] == "front":
        if len(deq) == 0:
            print(-1)
        else:
            print(deq[0])
    elif a[0] == "back":
        if len(deq) == 0:
            print(-1)
        else:
            print(deq[-1])