#include<bits/stdc++.h>
using namespace std;
int n;
queue<int> a;
int main(){
	cin>>n;
	while(n--){
	    int ds;
	    cin>>ds;
	    if(ds==1){cin>>ds;a.push(ds);}
	    else if(ds==2){
	    	if(a.size()==0)cout<<"ERR_CANNOT_POP\n"; 
		    else a.pop();
		}
	    else if(ds==3){
	    	if(a.size()==0)cout<<"ERR_CANNOT_QUERY\n";
	    	else cout<<a.front(); 
		}
		else cout<<a.size()<<"\n";
	}
}