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 ll long long
#define rep(i, n) for(ll i = 0; i < n; i++)
using namespace std;
int dy[4] = { 1, 0, -1, 0 }, dx[4] = { 0, 1, 0, -1 };
const ll MOD = 1e9 + 7;
const ll INF = 1e9;
unsigned gcd(unsigned a, unsigned b) {
    while (1) {
        if (a < b) swap(a, b);
        if (!b) break;
        a %= b;
    }
    return a;
}

int main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll a, b, c, d;
  cin >> a >> b >> c >> d;
  ll ans;
  ll e = c * d / gcd(c, d);
  ans = (b-a+1) - (b/c - (a-1)/c) - (b/d - (a-1)/d) + (b/e - (a-1)/e);
  cout << ans << endl;
  return 0;
}