#include<cstdio>
#include<queue> 
using namespace std;
int n,op,x;
queue<int>q; 
int main(){
	scanf("%d",&n);
	while(n--){
		scanf("%d",&op);
		if(op==1){
			scanf("%d",&x);
			q.push(x);
		}
		else if(op==2){
			if(q.empty())printf("ERR_CANNOT_POP\n");
			else q.pop();
		}
		else if(op==3){
			if(q.empty())printf("ERR_CANNOT_QUERY\n");
			else printf("%d\n",q.front());
		}
		else printf("%d\n",q.size());
	}
	return 0;
}