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;
using System.Linq;
using System.Collections.Generic;
using static System.Console;
using static System.Math;
 
public class Hello{
    public static void Main(){
        string[] read = ReadLine().Split(' ');
//        int read_leng = read.Length;
//        int[] readR = new int[mochinum];
        long a = long.Parse(read[0]);
        long b = long.Parse(read[1]);
        long c = long.Parse(read[2]);
//        int d = int.Parse(read[3]);
        long ans=0;
        if(a == 0){
            ans++;
            a++;
        }
        long min = a/c;
        if(a % c > 0){
            min++;
        }
        long max = b/c;
//        WriteLine($"{ans} {max} {min}");
        WriteLine(ans+max-min+1);
    }
}