class MyQueue

 {

     private Stack s1;

     private Stack s2;

     public MyQueue(int size)

     {

         this.s1 = new Stack(size);

         this.s2 = new Stack(size);

     }

     public boolean isFull()

     {

         return s1.isFull();

     }

     public boolean isEmpty()

     {

         return s1.isEmpty();

     }

     //时间复杂度: O(n)

     public void EnQueue(int k) throws Exception

     {

         if(s1.isFull())

             throw new Exception("Overflow.");

         else

         {

             while(!s1.isEmpty())

                 s2.push(s1.pop());

             s1.push(k);

             while(!s2.isEmpty())

                 s1.push(s2.pop());

         }

     }

     //时间复杂度: O(1)

     public int DeQueue() throws Exception

     {

         if(s1.isEmpty())

             throw new Exception("Underflow.");

         else

             return s1.pop();

     }

 }

 class Stack

 {

     private int top;

     private int[] a;

     public Stack(int size)

     {

         this.top = -1;

         this.a = new int[size];

     }

     public boolean isFull()

     {

         return this.top == this.a.length - 1;

     }

     public boolean isEmpty()

     {

         return this.top == -1;

     }

     public void push(int k) throws Exception

     {

         /*if(this.isFull())

             throw new Exception("Overflow.");*/

         //else

             this.a[++top] = k;

     }

     public int pop() throws Exception

     {

         /*if(this.isEmpty())

             throw new Exception("Underflow.");*/

         //else

             return this.a[top--];

     }

     public int getLength()

     {

         return this.top + 1;

     }

 }