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;

namespace Test
{
	class MainClass
	{
		public static void Main(string[] args)
		{
			// 半角スペース区切り
			string[] input = Console.ReadLine().Split(' ');
			ulong a = ulong.Parse(input[0]);
			ulong b = ulong.Parse(input[1]);
			ulong x = ulong.Parse(input[2]);
			ulong i = a / x;
			if (a % x > 0)
			{
				i++;
			}
			ulong j = b / x;
			if (i > j)
			{
				Console.Write((0));
			}
			else
			{
				//出力
				Console.Write((j - i + 1));
			}
		}
	}
}