你敢点进来么

/*
3、 B3616 【模板】队列
*/
#include<bits/stdc++.h>
using namespace std;
queue <int> q;
int main(){
	int n,x,s;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>s;
		if(s==1){
			cin>>x;
			q.push(x);
		}
		if(s==2){
			if(!q.empty())q.pop();
			else cout<<"ERR_CANNOT_POP"<<endl;
		}
		if(s==3){
			if(!q.empty())cout<<q.front();
			else cout<<"ERR_CANNOT_QUERY"<<endl;
		}
		if(s==4)cout<<q.size()<<endl;
		while(!q.empty())q.pop();
	}
	return 0;
}