#include<bits/stdc++.h>
using namespace std;
using ll=long long;
const int N=1e6+10,inf=1e9+10;
const ll INF=1e18+10;
class Deque{
    private:
        struct node{
            int x;
			node *pst,*nxt;
        };
        node *head,*tail;int len=0;
    public:
        Deque(){
            node h,t;
            head=&h,tail=&t;
            head->nxt=tail;
            tail->pst=head;
        }
        void push_back(int x){
            node n={x,tail->pst,tail};
            cout<<head<<" "<<n.pst<<" "<<tail->pst<<endl;
            n.pst->nxt=&n;
            tail->pst=&n;
            len++;
            return;
        }
        void push_front(int x){
            node n={x,head,head->nxt};
            n.nxt->pst=&n;
            head->nxt=&n;
            len++;
            return;
        }
        void pop_back(){
            tail->pst=tail->pst->pst;
            tail->pst->nxt=tail;
            return;
        }
        void pop_front(){
            head->nxt=head->nxt->nxt;
            head->nxt->pst=head;
            return;
        }
        int size(){
            return len;
        }
        int front(){
            return head->nxt->x;
        }
        int back(){
            return tail->pst->x;
        }
        bool empty(){
            return !len;
        }
};
Deque q[N];
int main(){
//     freopen("train.in","r",stdin);
    // freopen("train.out","w",stdout);
//    ios::sync_with_stdio(0);
//    cin.tie(0);cout.tie(0);
    int t;
    cin>>t;
    while(t--){
        string op;int i;
        cin>>op>>i;
    	cout<<t<<'\n';
        if(op=="push_back"){
            int x;
            cin>>x;
            q[i].push_back(x);
        }
        if(op=="push_front"){
            int x;
            cin>>x;
            q[i].push_front(x);
        }
        if(op=="pop_back"&&q[i].size())
            q[i].pop_back();
        if(op=="pop_front"&&q[i].size())
            q[i].pop_front();
        if(op=="size")
            cout<<q[i].size()<<'\n';
        if(op=="front"&&q[i].size())
            cout<<q[i].front()<<'\n';
        if(op=="back"&&q[i].size())
            cout<<q[i].back()<<'\n';
    }
    return 0;
}