Why does the program run the lines after line 13 : I want to make a program that gets a number input and finds the closest perfect square to determine the square length. Thus, the closest perfect square has to be less than the input. For example, if the input is 8, the largest side length of the square is 2. 

import java.util.Scanner;  
public class J1 {

	public static void main(String[] args) {

		int a;
		int a1;

		Scanner number = new Scanner(System.in);
		System.out.println("Number: ");
		a = number.nextInt(); 
		int n = (int) Math.sqrt(a1); 


		for (int a1=a; a1<a; a1--) {

			if (Math.floor(a1)==0)
			System.out.println("The largest square has side length" + a1); 

		}
	}
}