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: Wrong Answer)

// Original: https://github.com/tanakh/competitive-rs
#[allow(unused_macros)]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };

    ($next:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, [ $t:tt ]) => {
        {
            let len = read_value!($next, usize);
            (0..len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
        }
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, bytes) => {
        read_value!($next, String).into_bytes()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

#[allow(unused_imports)]
use std::cmp::{max, min};
#[allow(unused_imports)]
use std::collections::BTreeMap;

fn main() {
    input!(a: usize, b: usize, c: usize, d: usize);
    let total = b;
    let c_mlt = total / c;
    let d_mlt = total / d;
    let cd_mlt = total / (c / gcd(c, d) * d);
    let ans1 = total - (c_mlt + d_mlt - cd_mlt);

    let left = a;
    let c_mlt_l = a / c;
    let d_mlt_l = a / d;
    let cd_mlt_l = left / (c / gcd(c, d) * d);
    let ans2 = left - (c_mlt_l + d_mlt_l - cd_mlt_l);
    println!("{}", ans1 + 1 - ans2);
}

pub fn gcd<T>(x: T, y: T) -> T
where
    T: PartialEq + Copy + std::ops::Rem<Output = T> + std::convert::From<u8>,
{
    if y == T::from(0u8) {
        x
    } else {
        gcd(y, x % y)
    }
}

/// Finds a solution of Bézout's identity ``s * x + t * y = d``
/// where `d` is the greatest common divisor of `x`, `y`.
pub fn gcd_ext(x: i64, y: i64) -> (i64, i64, i64) {
    if y == 0 {
        (x.abs(), x.signum(), 0)
    } else {
        let (d, s, t) = gcd_ext(y, x % y);
        (d, t, s - x / y * t)
    }
}