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 Java (OpenJDK 11.0.6) (judge verdict: Runtime Error)

import java.util.Scanner;

class Main{

  /** 入力値A */
  private static int a;

  /** 入力値B */
  private static int b;

  /** 入力値X */
  private static int X;

  /**
   * メインメソッド
   *
   * @param args 実行時引数
   */
  public static void main(String[] args) {
    inputDate();
    System.out.println(getCount(b) - getCount(a - 1));
  }

  /** 入力値設定 */
  private static void inputDate() {
    var sc = new Scanner(System.in);
    a = sc.nextInt();
    b = sc.nextInt();
    X = sc.nextInt();
  }

  /**
   * Xで割り切れる数を取得
   *
   * @param targetNum 数値
   * @return count 個数
   */
  private static int getCount(int targetNum) {

    // a == 0 の場合
    if (targetNum == -1) {
      return 0;
    } else {
      return targetNum / X + 1;
    }
  }
}