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

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