#include <iostream>
#include <deque>
#include <cstring>
using namespace std;
 
int main (){
	deque<int> deque;
	string S;
	int N;
 
	while (cin >> S){
		if (S == "size")	cout << deque.size() << endl;
		else if (S == "back")	cout << deque.back() << endl;
		else if (S == "front")	cout << deque.front() << endl;
		else if (S == "push_front"){
			cin >> N;
			deque.push_front(N);
			cout << "ok" << endl;
		}
		else if (S == "push_back"){
			cin >> N;
			deque.push_back(N);
			cout << "ok" << endl;
		}
		else if (S == "pop_front"){
			cout << deque.front() << endl;
			deque.pop_front();
		}
		else if (S == "pop_back"){
			cout << deque.back() << endl;
			deque.pop_back();
		}
		else if (S == "clear"){
			deque.clear();
			cout << "ok" << endl;
		}
		else if (S == "exit"){
			cout << "bye" << endl;	
			return 0;
		}
	}
 
	return 0;
}

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push_back 3
push_front 14
size
clear
push_front 1
back
push_back 2
front
pop_back
size
pop_front
size
exit