#include <stack>

#include <iostream>

using namespace std;

class Queue

{

public:

void enQueue(int x)

{

//push item onto the first stack

s1.push(x);

}

int deQueue()

{

if (s1.empty() && s2.empty())

{

cout << "queue is empty" << endl;

return -1;

}

//if s2 is empty, move all items from s1

if (s2.empty())

{

while(!s1.empty())

{

s2.push(s1.top());

s1.pop();

}

}

//return top item from s2

int x = s2.top();

s2.pop();

return x;

}

private:

stack<int> s1, s2;

};

int main()

{

Queue q;

q.enQueue(1);

q.enQueue(2);

q.enQueue(3);

cout << q.deQueue() << endl;

cout << q.deQueue() << endl;

cout << q.deQueue() << endl;

return 0;

}