#include <iostream>
#include <string>
#include <deque>
#include <algorithm>

using namespace std;
int n;
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    deque<int> dq;

    cin >> n;
    
    while(n--) {
        string s;
        cin >> s;
        if(s=="push_front") {
            int x;
            cin >> x;
            dq.push_front(x);
        } else if(s=="push_back") {
            int x;
            cin >> x;
            dq.push_back(x);
     
        } else if(s=="pop_front") {
            if(dq.empty()) cout << -1 <<'\n';
            else {
                int a=dq.front();
                dq.pop_front();
                cout << a <<'\n';
            }
        } else if(s=="pop_back") {
            if(dq.empty()) cout << -1 <<'\n';
            else {
                int a=dq.back();
                dq.pop_back();
                cout << a <<'\n';
            }
       
        } else if(s=="size") {
            cout << dq.size() << '\n';
        } else if(s=="empty") {
            cout << dq.empty() << '\n';
        } else if(s=="front") {
            if(dq.empty()) cout << -1 <<'\n';
            else cout << dq.front() << '\n';
        } else if(s=="back") {
            if(dq.empty()) cout << -1 <<'\n';
            else cout << dq.back() << '\n';
        }
    }
}