题解

#include <iostream>
#include<queue>
using namespace std;
int main(){
	queue<int> q;
	int n,m,p;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>m;
		if(m==1){
			cin>>p;
			q.push(p);
		}else if(m==2){
			if(q.empty()){
				cout<<"impossible!"<<endl;
			}else{
				q.pop();
			}
		}else if(m==3){
			if(q.empty()){
				cout<<"impossible!"<<endl;
			}else{
				cout<<q.front()<<endl;
			}
			
		}
	}
	return 0;
}