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