超简单题解

#include <iostream>
#include <queue>

using namespace std;
int main(){
queue <int> q;
int n;
cin >> n;
while(n--){
int a;
cin >> a;
if(a == 1){
int x;
cin >> x;
q.push(x);
}else if(a == 2 && !q.empty()){
q.pop();
}else if(a == 3 && !q.empty()){
cout << q.front() << endl;
}else {
cout << "impossible!" << endl;
}
}
return 0;
}