#include <bits/stdc++.h>
using namespace std;
int main()
{
	string a="LIN",b="RIN",c="LOUT",d="ROUT",m;
	int n,x;
	cin>>n;
	int temp=n; 
	deque <int> s;
	queue <int> p;
	while(n--)
	{
		cin>>m;
		if(m==a)
		{
			cin>>x;
			s.push_front(x);
		}
		else if(m==b)
		{
			cin>>x;
			s.push_back(x);
		}
		else if(m==c)
		{
			if(!s.empty()) 
			{
			s.pop_front();
		    }
		    else p.push(temp-n+1);
		}
		else if(m==d)
		{
		   if(!s.empty()) 
			{
		     s.pop_back();
		    }
		    else p.push(temp-n);	
		}
	} 
	while(!s.empty())
	{
		cout<<s.front();
		s.pop_front();
		s.empty()?cout:cout<<" "; 
	}
	cout<<endl;
	while(!p.empty())
	{
		cout<<p.front();
		p.pop();
		cout<<" ERROR"<<endl; 
	}
	
	return 0;
}