#include<bits/stdc++.h>
#include <queue>
using namespace std;
queue<int> s1;
int main ()
{
	int n,x;
	cin>>n;
	
	for(int i=1;i<=n;i++)
	{
		int a;
		cin>>a;
		if(a==1)
		{		
		cin>>x,s1.push(x);
		
		}
		if(a==2)
		{
			if(s1.empty())
			cout<<"ERR_CANNOT_POP"<<endl;
			else
			s1.pop();
		}
		if(a==3&&s1.empty())
		cout << "ERR_CANNOT_QUERY\n";
		else 
		cout <<s1.front()<<endl;
		if(a==4)
		cout<<s1.size()<<endl;
	}
	return 0;
}