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 std::io;

fn main() {
    let mut input_line:String = String::new();
    io::stdin().read_line(&mut input_line).expect("err");

    let inputs: Vec<&str> = input_line.split_whitespace().collect();

    let a = inputs[0].parse::<i64>().unwrap();
    let b = inputs[1].parse::<i64>().unwrap();
    let x = inputs[2].parse::<i64>().unwrap();

    let ans: i64 = f(b, x)-f(a-1, x);

    print!("{}", ans);
}

fn f(n: i64, x: i64) -> i64 {
   if n == -1{
       return 0;
   }else{
       return (n/x)+1;
   }
}