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)

package atcoder;

import java.util.Scanner;

/** https://atcoder.jp/contests/abc048/tasks/abc048_b */
public class Main {

  /**
   * メインメソッド
   *
   * @param args 実行時引数
   */
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    int X = sc.nextInt();

    System.out.println(solve(a, b, X));
  }

  private static int solve(int a, int b, int x) {
    if (a != 0) {
      return b / x - (a - 1) / x;
    } else {
      return b / x;
    }
  }
}