Problem:
Score : 200 points

Problem Statement

You are given nonnegative integers a and b (a ≤ b), and a positive integer x.
Among the integers between a and b, inclusive, how many are divisible by x?

Constraints

0 ≤ a ≤ b ≤ 10^{18}

1 ≤ x ≤ 10^{18}

Input

The input is given from Standard Input in the following format:

a b x

Output

Print the number of the integers between a and b, inclusive, that are divisible by x.

Sample Input 1

4 8 2

Sample Output 1

3

There are three integers between 4 and 8, inclusive, that are divisible by 2: 4, 6 and 8.

Sample Input 2

0 5 1

Sample Output 2

6

There are six integers between 0 and 5, inclusive, that are divisible by 1: 0, 1, 2, 3, 4 and 5.

Sample Input 3

9 9 2

Sample Output 3

0

There are no integer between 9 and 9, inclusive, that is divisible by 2.

Sample Input 4

1 1000000000000000000 3

Sample Output 4

333333333333333333

Watch out for integer overflows.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);

		long a = scan.nextLong();
		long b = scan.nextLong();
		long x = scan.nextLong();

		long kyu = 1000000000;


		long a1 = a / x;
		long b1 = b / x;

		long aa = a % x;
		long bb = b % x;

		if (aa == 0 && bb == 0) {

			System.out.println(b1 - a1 + 1);

		} else if (a == b) {

			if (aa == 0) {
				System.out.println(a1);
			} else if (aa > 0) {

				System.out.println(0);
			}
		}else if(b>kyu) {

			long ko=a/kyu;
			long ke=b/kyu;
			long koko=ko/x;
			long keke=ke/x;

			System.out.println((keke+keke*kyu)-(koko+koko*kyu));

		}else {
			System.out.println(b1-a1);
		}
	}

}