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)

use std::io::*;
use std::str::FromStr;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

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

fn main() {
    let a: i64 = read();
    let b: i64 = read();
    let c: i64 = read();
    let d: i64 = read();

    let g = gcd(c,d);
    let l = (c*d)/g;

    //全体 - cで割り切れる数(倍数)の個数 - dで割り切れる数(倍数)の個数 + c*dで割り切れる数(倍数)の個数
    let all = b - b/c - b/d + b/l;
    let a_made = (a-1) - (a-1)/c - (a-1)/d + (a-1)/l;

    println!("{}", all - a_made);
}