//#include<bits/stdc++.h>
#include<iostream>
#include<math.h>
#include<cstring>
#include<string.h>
#include<algorithm>
#include<stack>
#include<queue> 
#include<stdio.h>

using namespace std;

queue<int> q;
int n;

int main()
{
	cin>>n;
	for(int i=0;i<n;i++)
	{
		int s;
		cin>>s;
		if(s==1)
		{
			int m;
			cin>>m;
			q.push(m);
		}
		else if(s==2)
		{
			if(q.empty())
			{
				cout<<"ERR_CANNOT_POP\n";
			}
			else q.pop();
		}
		else if(s==3)
		{
			if(q.empty())
			{
				cout<<"ERR_CANNOT_QUERY\n";
			}
			else cout<<q.front()<<endl;
		}
		else if(n==4)cout<<q.size()<<endl;
	}
    return 0;
}