// Stack implementation using Queue
class QueueStack
{
    // Queue
    private System.Collections.Generic.Queue<int> q;

    public QueueStack()
    {
        q = new System.Collections.Generic.Queue<int>();
    }

    // Method to push element in the stack
    public void Push(int x)
    {
        // Get size
        int s = q.Count;
        // Add element
        q.Enqueue(x);

        // Move elements before new element to back
        for (int i = 0; i < s; i++)
        {
            q.Enqueue(q.Dequeue());
        }
    }

    // Method to pop element from stack
    public int Pop()
    {
        // Get front element and remove it
        return q.Dequeue();
    }

    // Method to return the top of stack
    public int Top()
    {
        // Return front element
        return q.Peek();
    }

    // Method to check if the stack is empty
    public bool IsEmpty()
    {
        return q.Count == 0;
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        QueueStack st = new QueueStack();

        // List of commands
        string[] commands = { "QueueStack", "push", "push", "pop", "top", "isEmpty" };
        int[][] inputs = { new int[] { }, new int[] { 4 }, new int[] { 8 }, new int[] { }, new int[] { }, new int[] { } };

        for (int i = 0; i < commands.Length; ++i)
        {
            switch (commands[i])
            {
                case "push":
                    st.Push(inputs[i][0]);
                    System.Console.WriteLine("null ");
                    break;
                case "pop":
                    System.Console.WriteLine(st.Pop() + " ");
                    break;
                case "top":
                    System.Console.WriteLine(st.Top() + " ");
                    break;
                case "isEmpty":
                    System.Console.WriteLine(st.IsEmpty() ? "true " : "false ");
                    break;
                case "QueueStack":
                    System.Console.WriteLine("null ");
                    break;
            }
        }
    }
}

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package main

import (
	"fmt"
)

// QueueStack implements a stack using a single queue
type QueueStack struct {
	q []int // underlying queue slice
}

// Constructor function
func NewQueueStack() *QueueStack {
	return &QueueStack{
		q: make([]int, 0), // initialize empty queue slice
	}
}
// Push element in the stack
func (st *QueueStack) push(x int) {
	// Get size
	s := len(st.q)
	// Add element
	st.q = append(st.q, x)

	// Move elements before new element to back
	for i := 0; i < s; i++ {
		front := st.q[0]
		st.q = st.q[1:]