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: Time Limit Exceeded)

#include <bits/stdc++.h>

using namespace std;
#define int long long
#define INF 1ll<<60
signed main(){
  int med,a,b,c,d,f,k=0,fb,g=0;
  cin>>a>>b>>c>>d;
  f=a;
  med=b-a;

  while(f%c!=0 && f<b){
    f++;
    if(f%d==0 && g==0 ){
      fb=f;
      g++;
    }
  }
  f=b-f;
  k=med - (f/c);
  f=a;
  if(g==1){
    f=fb;
  }else{
    while(f%d!=0 && f<=b){
      f++;
    }
  }
  while(f%d==0 && f<=b){
    if(f%c!=0){
      k--;
    }
    f+=d;
  }
  cout<<k<<endl;

}