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 long fgcd(long long a, long long b) {
  long long x=min(a, b), y=max(a, b);
  if (y%x==0) return b;
  return fgcd(x, y%x);
}

int main() {
  long long a, b, c, d;
  cin >> a >> b >> c >> d;
  a--;
  long long lcm=c*d/fgcd(c, d);
  if (c==d) {
    cout << (b-b/c)-(a-a/c) << endl;
    return 0;
  }
  cout << (b-b/c-b/d+b/lcm)-(a-a/c-a/d+a/lcm) << endl;
}