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