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: Wrong Answer)

using System;
using System.Linq;

namespace B_Between
{
    class Program
    {
        static void Main(string[] args)
        {
            var inputs = Console.ReadLine().ToLongArray();
            var a = inputs[0];
            var b = inputs[1];
            var x = inputs[2];

            var small = Math.Max((a - 1), 0) / x;
            var big = b / x;

            Console.WriteLine(big -small);
        }
    }
    
    static class StringExtention
    {
        static public int ToInt(this string input)
        {
            return int.Parse(input);
        }

        static public int[] ToIntArray(this string input)
        {
            return input.Split(' ').Select(int.Parse).ToArray();
        }

        static public long ToLong(this string input)
        {
            return long.Parse(input);
        }

        static public long[] ToLongArray(this string input)
        {
            return input.Split(' ').Select(long.Parse).ToArray();
        }
    }
}