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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

var reader = require('readline').createInterface({
    input: process.stdin,
    output: process.stdout
});

var args = [];

reader.on('line', function (input) {
  args.push(input);
});


reader.on('close', function () {
    var str = args[0].split(" ");
    var num = [];
    var count = 0;
    for(var i = 0; i < str.length; i++){
        num[i] = parseInt(str[i]);
    }
    while (num[0] % num[2] !== 0) {
        num[0]++;
        if(num[0] >= num[1]){
            break;
        }
    }
    for(num[0]; num[0] <= num[1]; num[0] += num[2]){
        count++;
    }
    console.log(count);
});