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: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
#define all(a) (a).begin(),(a).end()
#define ll long long
int main(){
  ll A,B,C,D;
  cin>>A>>B>>C>>D;
  ll CC,CC2,DD,DD2,CD,CD2;
  
  CC=B/C;
  CC2=(A-1)/C;
  CC-=CC2;
  
  DD=B/D;
  DD2=(A-1)/D;
  DD-=DD2;
  
  vector<ll> Q(2);
  Q[0]=min(C,D),Q[1]=max(C,D);
  while(Q[0]!=0){
    Q[1]%=Q[0];
    sort(all(Q));
  }
  ll X=C*D/Q[1];
  CD=B/X;
  CD2=(A-1)/X;
  CD-=CD2;
  
  cout<<B-A+1-CC-DD+CD<<endl;
}