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;

//using Matrix = vector< vector<int> >;
typedef long long ll;
typedef pair<int, int> P;
const int INF = 1e9 + 10;
//const ll INF = 1e18 + 10LL;
int dx[5] = {0, 0, 1, -1, 0}, dy[5] = {1, -1, 0, 0, 0};
const double EPS = 1e-10;
bool cmp(P a, P b) { return a.second < b.second; } //End sort (Interval scheduling problem)
ll MOD = 1e9 + 7;

ll a, b, c, d;

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

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

ll solve(ll a, ll b, ll c, ll d) {
	ll B = (b / c + b / d) - (b / lcm(c, d));
	ll A = (a / c + a / d) - (a / lcm(c, d));

	if (a % c == 0 || a % d == 0) return (b - a + 1) - (B - A + 1);
	return (b - a + 1) - (B - A);
}

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

	cout<< solve(a, b, c, d) <<endl;
	
	return 0;
}