#include <bits/stdc++.h>
using namespace std;
queue<int>ppp;
int x,y,n; 
int main(){
	cin>>n;
	for(int i=0;i<n;i++){
		cin>>x;
		switch(x){
			case 1 :
				cin>>y;
				ppp.push(y);
				break;
			case 2 :
				if(ppp.empty())cout<<"ERR_CANNOT_POP"<<endl;
				else ppp.pop();
				break;
			case 3 :
				if(ppp.empty())cout<<"ERR_CANNOT_QUERY"<<endl;
				else cout<<ppp.front()<<endl;
				break;
			case 4 :
				cout<<ppp.size()<<endl;
				break;
		}
	}
	return 0;
}