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>
#define _GLIBCXX_DEBUG
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()

using namespace std;
using ll = long long;
using vpii = vector<pair<int, int>>;
using vpll = vector<pair<ll, ll>>;
// ceil() 切り上げ, floor() 切り捨て
// next_permutation(all(x))

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

ll lcm(ll a, ll b)
{
   return a * b / gcd(a, b);
}

int		main(void)
{
	ll a, b, c, d;
	cin >> a >> b >> c >> d;

	ll mul_c = b / c - (a-1) / c;
	ll mul_d = b / d - (a-1) / d;
	ll lcm_cd = lcm(c, d);
	ll mul_lcm = b / lcm_cd - (a-1) / lcm_cd;
	cout << (b-a+1) - mul_c - mul_d + mul_lcm << endl;
}