Handling Large Numbers

I found an exercise online to create a small program . I have this code that I have done so far:

import java.util.Scanner;
public class Test {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
long a = sc.nextLong(); long b = sc.nextLong();
long count = 0; // counter

[code]....

The program should read the numbers a and b and list how many numbers between a and b are divisible by either 2, 3 or 5. If the user types the number 5 and then 8.... it would look at all the numbers in between - 5,6,7,8 and check if any of them are divasable by either 2,3 or 5. And since the numbers 5,6,8 are it would return the number 3 to the user..Now the problem is that this program only works for small numbers, but when I try to input numbers such as 123456789012345678 and 876543210987654321... it doesn't run at all.

So there needs to be a quicker way on how the program checks the numbers divisibility instead of checking each one. Here is where I am lost. How to fix the program that it will read bigger numbers such as a=123456789012345678 b=87654321098765432..There must be a quicker way ...something that can modify the code so it finishes in the matter of seconds not hours. Something that will fasten the process of checking if the numbers are dividable.