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 Kotlin (1.3.71) (judge verdict: Wrong Answer)

fun main() {
    val (a, b, x) = readLine()!!.split(" ").map { it.toLong() }

    if (a == b) {
        val answer = if (a % x == 0L) 1 else 0
        print(answer)
        return
    }
    var min = a
    for (i in a until b) {
        if (i % x == 0L) {
            min = i
            break
        }
    }

    if (b < x) {
        print(0)
        return
    }

    print(1 + (b - min) / x)
}