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<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<cmath>
using namespace std;

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

int main()
{
 long long a,b,c,d,lcm,div,aan,ban;
 aan=-1;
 ban=-1;
 cin>> a >> b >> c >> d;
 lcm=c*d/gcd(c,d);
 div=lcm-(lcm/c+lcm/d-1);
 aan+=div*(a/lcm);
 ban+=div*(b/lcm);
 for(int i=0;i<(a-1)-(a-1)/lcm*lcm+1;i++){
   if((i%c!=0)&&(i%d!=0)) aan++;
 }
 for(int i=0;i<b-b/lcm*lcm+1;i++){
   if((i%c!=0)&&(i%d!=0)) ban++;
 }
 cout<<ban-aan;
  return 0;
}