Give Number Of Numbers Dividable By Either 2 / 3 Or 5 In A Range

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
for (long c = a; c <= b; c++) {
if (c % 2 == 0 || c % 3 == 0 || c % 5 == 0) {
count++;
}
}
System.out.println(count);
}
}

This program is suppose to give me the number of numbers which are dividable by either 2,3 or 5 in a range of a to b, where a<=b.

FOR EXAMPLE: a=5 b=8 ... output: 14 (since there are 14 numbers in between 5 and 8 which are dividable by either 2,3 or 5.)

It works great for all of the numbers except higher ones such as a=123456789012345678 b=876543210987654321. Here it doesn't give me any output. From what I know it is because the code is still running. But 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...