#include <iostream>
#include <queue>
using namespace std;
int main()
{
    queue <int> s;

    char c;
    int y;
    while (true){
        cin>>c>>y;

        if (c=='a'){
            s.push(y);
        }

        if (c=='d'){
            if(!s.empty()) {
                cout<<s.front()<<endl;
                 s.pop();
            }
            else{
                    cout<<"the stack is empty"<<endl;
                    break;
            }
        }

        if ((c!='a') && (c!='d')) {
            while(!s.empty()){
                cout<<s.front()<<endl;
                s.pop();
            }
            break;
        }
    }

    return 0;

    }