#include<bits/stdc++.h>
using namespace std;
int n,s,x;
queue<int>q;
int main(){
    freopen("1.in","r",stdin);
    cin>>n;
    while(n--){
        scanf("%d",&s);
        switch(s){
            case 1:scanf("%d",&x),q.push(x);break;
            case 2:{
                if(q.empty())puts("ERR_CANNOT_POP");
                else q.pop();
                break;
            }
            case 3:{
                if(q.empty())puts("ERR_CANNOT_QUERY");
                else printf("%d\n",q.front());
                break;
            }
            case 4:printf("%d\n",q.size());break;
        }
    }
    return 0;
}

全WA，说是第一行太短，搞不懂为什么，求dl帮助