#include <iostream>
#include <string>
using namespace std;
const int s = 100000;
int d [s], f, l;
int r_i (int i){
    return ((i%s +s)%s);
}
void push_front (int x){
    d [r_i(f)] = x;
    --f;
    cout << "ok" << endl;
}
void push_back (int x){
    d [r_i(l)] = x;
    ++l;
    cout << "ok" << endl;
}
int pop_front (int x){
    return (r_i(f));
    f++;
}
int pop_back (){
    return (r_i(l));
    --l;
}
int back (){
    return (d[r_i(l-1)]);
}
int front (){
    return (d[r_i(f+1)]);
}
int size (){
    return (l-f-1);
}
bool empty (){
    return (size() == 0);
}
void clear (){
    while (!empty){
        pop_back;
    }
    cout <<"ok"<< endl;
}
void exit(){
    cout <<"bye"<<endl;
}
int main(){
    string b;
    int a, c, d, e, f;
    while true{
        cin >> n;
        switch n:
            case ("push_front")
            {
                cin >> a;
                push_front (a)
            }
            case ("push_back")
            {
                cin >> c;
                push_back (c)
            }
            case ("push_front")
            {
                cin >> d;
                push_front (d)
            }
            case ("pop_front")
            {
                pop_front ()
            }
            case ("pop_back")
            {
                pop_back ()
            }
            case ("back")
            {
                cout<<back;
            }
            case ("front")
            {
                cout<<front;
            }
            case ("exit")
            {
                exit ()

            }
            case ("clear")
            {
                cin >> a;
                push_front (a)
            }
    }
}