class FIFO private LIFO l1 LIFO l2 public void enqueue int l1 push int

class FIFO
{
private:
    LIFO l1;
    LIFO l2;
public:
    void enqueue(int n)
    {
        l1.push(n);
    }
    
    int isempty()
    {
        return l1.isempty() && l2.isempty();
    }
    
    int dequeue()
    {
        if (l2.empty())
        {
            while (!l1.empty())
            {
                l2.push(l1.pop());
            }
        }
        return l2.pop();
    }
};