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