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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

long gcd(long a, long b) {
    if (b == 0) {
        return a;
    } else {
        return gcd(b, a % b);
    }
}

long lcm(long C, long D) {
    return C * D / gcd(C, D);
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    long A, B, C, D;
    cin >> A >> B >> C >> D;

    long min_Cx = 0, min_Dx = 0, min_CDx = 0;

    if (A % C == 0) {
        min_Cx = A;
    } else {
        min_Cx = A + C - (A % C);
    }

    if (A % D == 0) {
        min_Dx = A;
    } else {
        min_Dx = A + D - (A % D);
    }

    long lcm_CD = lcm(C, D);

    if (A % lcm_CD == 0) {
        min_CDx = A;
    } else {
        min_CDx = A + lcm_CD - (A % lcm_CD);
    }

    cout << B - A + 1 - (B - min_Cx) / C - 1 - (B - min_Dx) / D - 1 + (B - min_CDx) / lcm_CD + 1 << "\n";
    return 0;
}