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: Accepted)

use std::env;
use std::io::*;
use std::str::*;
use std::mem;
use std::collections::HashMap;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let s = stdin.bytes().map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    s.parse::<T>().ok().unwrap()
}
fn read_char() -> char {
    let c = read::<String>();
    let c = c.chars().collect::<Vec<char>>();
    c[0]
}
fn read_String_Vec() -> Vec<char> {
    let S = read::<String>();
    S.chars().collect::<Vec<char>>()
}

fn vecchar_to_String(Vs: Vec<char>) -> String {
    let mut S = String::new();
    for i in 0..Vs.len() {
        S.push(Vs[i]);
    }
    S
}

/*
A : 65
Z : 90
a : 97
z : 122
*/

/*
let N = read::<i32>();
let S = read::<String>();
let S = read_String_Vec();
let C = read_char();
*/

/*
 .to_string() : * -> String
 &*S          : String -> &str
*/

fn main() {
    // main の引数
    /*
        引数なしのときargs.len() = 1;
    */
    let args: Vec<String> = env::args().collect();

    let a = read::<i64>();
    let b = read::<i64>();
    let x = read::<i64>();

    /*
        5 12 3
        6, 9, 12
    */
    let upper = b / x;
    let bottom = {
        if a%x == 0 {
            a/x
        } else {
            a / x + 1
        }
    };
    println!("{}", upper - bottom+1);
}