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 Scala (2.11.7) (judge verdict: Wrong Answer)

object Main extends App {
  val inputs: Seq[String] = scala.io.Source.stdin.getLines().toList
  
  val nums = inputs.head.split(" ").map(_.toLong)
  val a = nums(0)
  val b = nums(1)
  val x = nums(2)

  println(solve(a, b, x))

  private def solve(a: Long, b: Long, x: Long): Long = {
    val sur = a % x
    val firstDiv = a + sur

    if (b < firstDiv) {
      return 0
    }

    return (b - firstDiv) / x + 1
  }
}