import java.util.*;

public class Template {
    static int max_size;
    static int top ;
    int temp;
    static int arr[];
public void Stack(int size) {
         arr = new int[size];
         max_size = arr.length;
         top = -1;
    }

    public boolean empty() {          //checking if stack is empty .
        return temp  == -1;
    }

    public boolean full() {  //checking if stack is full .
        return top + 1 == max_size;
    }

    public void push(int Ip) {//PUSH operation
        if(top <= max_size) {
        top++;
        }
        try {                           //bit of exception handling while insertion/PUSH operation
            if(top >max_size) {
                throw new ArrayIndexOutOfBoundsException();       
            }
            else if(empty()|| top<=max_size) {
            arr[top] = Ip; 
            }
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Stack overflow");
            top--;
        }   
    }


    public void pop() {   // POP 
         temp = top;
    if(top > -1) {           // stop top from further decrementing if already -1,
        top--;              // if not it will interfere with push operation.
        }else { temp--;}        
    try {                       //bit of exception handling while deletion/POP operation
        if(temp < -1) throw new ArrayIndexOutOfBoundsException();
    }catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Stack underflow");  

    }
    }

    public void Top()
    {
         System.out.println(arr[top] +" at index "+ top);
    }


    public static void main(String[] args)
    {

        Template t = new Template();
        t.Stack(4);
        t.push(6);
        t.Top(); // <---- Return Top variable of Stack
        t.pop(); // <--- 6 is removed from the stack so stack will be empty
        t.pop(); // <-- so removing element from empty stack will return "UNDERFLOW"
        t.push(101);
        t.Top(); // <---- Return Top variable of Stack
        t.push(10);
        t.Top(); // <---- Return Top variable of Stack
        t.push(112);   
        t.Top();    // <---- Return Top variable of Stack
        t.push(14); //<----- stack will be full at this point
        t.Top();
        t.push(146); // so if you push anything it will print "OVERFLOW"
        t.push(110);
        t.Top(); // <---- Return Top variable of Stack
    }

}