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