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;

int main() {
  int64_t A, B, C, D;
  cin >> A >> B >> C >> D;
  int64_t c = C;
  int64_t d = D;
  if (C > D)
  swap(C, D);
  int64_t r = C % D;
  int64_t mul = C * D;
  while (r != 0){
    C = D;
    D = r;
    r = C % D;
  }
  int64_t lcm = mul / D;
  int64_t aquo = A / lcm;
  int64_t bquo = B / lcm;
  int64_t are = A % lcm;
  int64_t bre = B % lcm;
  int64_t cnt = lcm - (lcm / c) - (lcm / d) + 1;
  int64_t head = are - 1 - ((are - 1) / c) - ((are - 1) / d);
  int64_t tail = bre - (bre / c) - (bre / d);
  cout << (bquo - aquo) * cnt - head + tail << endl;
}