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)

macro_rules! bind_from_vec {
    ( $($variable:ident),+ = $vector: expr ) => {
        let mut v = $vector.clone().into_iter();
        $(let $variable = v.next().unwrap();)+
    };
}

macro_rules! read_line {
    () => {{
        let mut input = String::new();
        std::io::stdin().read_line(&mut input).unwrap();
        input
    }};
}

fn read_to_vec<T: std::str::FromStr>() -> Vec<T> {
    read_line!().split_whitespace()
        .map(|e| e.parse::<T>().ok().unwrap())
        .collect()
}

fn main() {
    bind_from_vec!(a, b, x = read_to_vec::<i64>());

    println!("{}", b/x + 1 - std::cmp::max((a-1)/x, 0));
}