#include <iostream>

using namespace std;

struct Node {
    int val;
    Node *next;
    Node(int x): val(x), next(NULL){}
};

struct Queue {
    Node *front;
    Node *rear;
    Queue() {
        front = rear = new Node(-1);
    }
};

bool isEmpty(Queue *q) {
    return q->front->next == NULL;
}

void join(Queue *q, int x) {
    Node *node = new Node(x);
    q->rear->next = node;
    q->rear = node;
}

void quit(Queue *q) {
    if(!isEmpty(q)) {
        Node *p = q->front->next;
        q->front->next = p->next;
        if(q->rear == p)
            q->rear = q->front;
        delete p;
    }
}

void print(Queue *q) {
    while(!isEmpty(q)) {
        cout << q->front->next->val << " ";
        quit(q);
    }
    cout << endl;
}

int main() {
    Queue *q = new Queue();
    join(q, 1);
    join(q, 2);
    join(q, 3);
    print(q);

    return 0;
}