public class Queue<T>
{
    private Node<T> first;
    
    public Queue() {
        first = null;
    }
    
    public boolean isEmpty() {
        if (first == null) return true;
        return false;
    }
    
    
    
    public T front(int n) {
        
     Node<T> current = first;
        
        for (int i = 0; i < n; i++) {
            if (current == null) return null;
            current = current.next;
        }
        
        if (current == null) return null;
        return current.wert;
    }
    
    public void enqueue(T val) {
        Node<T> neu = new Node<T>();
        neu.wert = val;
        
        if (first == null) {
            first = neu;
        } else {
            Node<T> current = first;
            while (current.next != null) {
                current = current.next;
            }
            current.next = neu;
        }
    }
    
   
    
  
    
    public T dequeue() {
       T tmp = first.wert;
       first = first.next;
       return tmp;
      
    }
    
    public String toString(){
        String result = "";
        Node<T> current = first;
        while (current != null) {
            result += current.wert + ", ";
            current = current.next;
        }
        return result;
    }
}