队列练习3

#include<cstdio>
#include<iostream>
#include<queue>
using namespace std;
int n,k,a;
int main()
{
    queue<int>line;
    cin>>n;
    while(n--)
    {
        cin>>k;
        if(k==1)
        {
            cin>>a;
            line.push(a);
        }
        if(k==2)
        {
            line.pop();
        }
        if(k==3)
        {
            cout<<line.front()<<endl;
        }
    }
//    if(line.empty())  cout<<"impossible!"<<endl;
//    else   cout<<line.front()<<endl;
    return 0;    
}