#include <iostream>

using namespace std;

struct Node
{
	int data;
	Node* pNext;
};

struct list
{
	Node* pHead;
	Node* pTail;
};

void khoaitao(list& l)
{
	l.pHead=NULL;
	l.pTail=NULL;
}
Node* getNode(int x)
{
	Node* p= new Node;
	if(p==NULL)
		return NULL;
	else {
		p->data=x;
		p->pNext=NULL;
	}
}

void addHead(list &l, Node* p)
{
	if(l.pHead==NULL)
		l.pHead=l.pTail=p;
	else {
		p->pNext=l.pHead;
		l.pHead=p;
	}
}

void addTail(list &l, Node* p)
{
	if(l.pHead==NULL)
		l.pHead=l.pTail=p;
	else {
		l.pTail->pNext=p;
		l.pTail=p;
	}
}

void addAfter(list &l, int x, int y)
{
	Node* p;
	for(p=l.pHead;p!=NULL;p->pNext)
	{
		if(p->data==x)
		{
			Node* t=getNode(y);
			p->pNext=t->pNext;
			p->pNext=t;
			t->data=y;
			break;
		}
		else addHead(l,p);
	}
}
void xuat(list l)
{
	for(Node* p=l.pHead;p!=NULL;p=p->pNext)
	{
		cout<<p->data;
	}
}

int main()
{
	list l;
	khoaitao(l);
	int x;
	do{
		cin>>x;
		if(x==3)
			break;
		else if(x==0)
		{
			int a;
			cin>>a;
			Node* p;
			addHead(l, p =getNode(a));
		}
		else if(x==1)
		{
			int b;
			cin>>b;
			Node* p;
			addTail(l,p=getNode(b));
		}
		else if(x==2)
		{
			int c,d;
			cin>>c;
			cin>>d;
			addAfter(l,c,d);
		}
	}while(x!=3);
	xuat(l);
	return 0;
}