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 Rust (1.42.0) (judge verdict: Accepted)

use proconio::input;

use std::cmp::*;
// use std::collections::*;
use proconio::marker::Chars;

fn main() {
    input! {
        a: u64,
        b: u64,
        x: u64,
    }
    // 0 なしで考える
    let v1 = if a == 0 { 0 } else { (a - 1) / x };
    let v2 = if b == 0 { 0 } else { b / x };
    let mut ans = v2 - v1;
    // 0 考慮
    if a == 0 {
        ans += 1;
    }
    println!("{}", ans);
}