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 (1.15.1) (judge verdict: Wrong Answer)

use std::io::prelude::*;
use std::io;

fn main() {
    let mut stdin = io::stdin();
    let mut buf = String::new();

    stdin.read_to_string(&mut buf).unwrap();

    let mut lines = buf.lines();

    let mut line = lines.next().unwrap().split_whitespace();
    
    let (a, b, x) = {
        let a: i64 = line.next().unwrap().parse().unwrap();
        let b: i64 = line.next().unwrap().parse().unwrap();
        let x: i64 = line.next().unwrap().parse().unwrap();
        (a, b, x)
    };
    
    let ans = if a % x == 0 && b % x == 0 {
        (b - a) / x + 1
    } else {
        (b - a) / x
    };
    
    println!("{}", ans);

}