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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
class Program
{
 static void Main(string[] args)
 {
  string[] sS = Console.ReadLine().Trim().Split(' ');
  long lA = long.Parse(sS[0]);
  long lB = long.Parse(sS[1]);
  long lX = long.Parse(sS[2]);
  long lOutA = lA / lX;
  long lOutB = lB / lX;
  long lAdd = 0;
  if (lA % lX == 0) { lAdd += 1; }
  long lOut = lOutB - (lOutA - lAdd);
  Console.WriteLine("{0}", lOut.ToString());
 }
}