interface IntStack {
    void push(int item);
    int pop();
}

class Stack implements IntStack {
    private int stck[];
    private int tos;

    Stack(int size) {
        stck = new int[size];
        tos = -1;
    }

    public boolean isEmpty(){
        if(tos > -1){
            return true;
        }
        return false;
    }

    // Push
    public void push(int item) {
        if(tos==stck.length-1)
            System.out.println("Stack is full.");
        else
            stck[++tos] = item;
    }

    // Pop
    public int pop() {
        if(tos < 0) {
            System.out.println("Stack underflow.");
            return 0;
        }
        else
            return stck[tos--];
    }
}


class Queue {
    Stack st1, st2;

    Queue(){
        st1 = Stack(5);
        st2 = Stack(5);
    }

    void enqueue(int x){
        st1.push(x);
    }

    int dequeue(){
        int x;
        while(!st1.isEmpty()){
            x = st1.pop();
            st2.push(x);
        }

        if(st2.isEmpty()){
            System.out.println("Queue underflow.");
        }
        x = st2.pop();
        while(!st2.isEmpty()){
            x = st2.pop();
            st1.push(x);
        }

        return x;
    }
}

class Main {
    public static void main(String[] args) {

    }
}