include <bits/stdc++.h>

define ll long long

define ld long double

using namespace std; int main(){

ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll n;
cin>>n;
deque<ll>dq;
for(int i = 0; i<n; i++){
    ll m, k;
    cin>>m;
    if(m == 1 || m == 2){
        cin>>k;
        if(m == 1){
            dq.push_front(k);
        }
        else if(m == 2){
            dq.push_back(k);
        }
    }
    if(m == 3){
        cout<<dq.front()<<endl;
        dq.pop_front();
    }
    else if(m == 4){
        cout<<dq.back()<<endl;
        dq.pop_back();
    }
}

}