Problem:
Score : 300 points

Problem Statement

You are given four integers A, B, C, and D. Find the number of integers between A and B (inclusive) that can be evenly divided by neither C nor D.

Constraints

1\leq A\leq B\leq 10^{18}

1\leq C,D\leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B C D

Output

Print the number of integers between A and B (inclusive) that can be evenly divided by neither C nor D.

Sample Input 1

4 9 2 3

Sample Output 1

2

5 and 7 satisfy the condition.

Sample Input 2

10 40 6 8

Sample Output 2

23

Sample Input 3

314159265358979323 846264338327950288 419716939 937510582

Sample Output 3

532105071133627368

Solution in Rust (1.15.1) (judge verdict: Accepted)

fn gcd(a:i64, b:i64) -> i64 {
    if a > b {
        gcd(b, a);
    }
    return if a == 0 { b } else { gcd(b % a, a) };
}

fn lcm(a:i64, b:i64) -> i64 {
    a * b / gcd(a,b)
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().split_whitespace()
        .map(|e| e.parse().ok().unwrap()).collect()
}

fn main() {
    let input_vec = read_vec::<i64>();
    let a = input_vec[0];
    let b = input_vec[1];
    let c = input_vec[2];
    let d = input_vec[3];
    //println!("A = {}", a);
    //println!("B = {}", b);
    //println!("C = {}", c);
    //println!("D = {}", d);
    let my_lcm = lcm(c, d);
    let until_a = (a - 1) - ((a - 1) / c) - ((a - 1) / d) + ((a - 1) / my_lcm);
    let until_b = b - (b / c) - (b / d) + (b / my_lcm);
    //println!("until a {}", until_a);
    //println!("until b {}", until_b);
    //println!("gcd {}", my_gcd);
    //println!("lcm {}", my_lcm);
    //println!("anwer {}", until_b - until_a);
    println!("{}", until_b - until_a);
}

// 10 40 6 8
// 23
//      1   2   3   4    5  6s  7   8o  9
// 10  11  12s 13  14   15 16o 17  18s 19
// 20  21  22  23  24so 25 26  27  28  29
// 30s 31  32o 33  34   35 36s 37  38  39
// 40o