标准题解

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