class MyStack {

// Push element x onto stack.

Queue<Integer> queue = new LinkedList<Integer>() ;

public void push(int x) {

queue.offer(x) ;

}

// Removes the element on top of the stack.

public void pop() {

Queue<Integer> tempQ = new LinkedList<Integer>() ;

while(!queue.isEmpty()) {

Integer i = queue.remove() ;

if (!queue.isEmpty())tempQ.offer(i) ;

}

while(!tempQ.isEmpty()) {

Integer i = tempQ.remove() ;

queue.offer(i) ;

}

}

// Get the top element.

public int top() {

int ans = -1 ;

Queue<Integer> tempQ = new LinkedList<Integer>() ;

while(!queue.isEmpty()) {

Integer i = queue.remove() ;

tempQ.offer(i) ;

if (queue.isEmpty()) ans = i ;

}

while(!tempQ.isEmpty()) {

Integer i = tempQ.remove() ;

queue.offer(i) ;

}

return ans ;

}

// Return whether the stack is empty.

public boolean empty() {

return queue.isEmpty() ;

}

}