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