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: Runtime Error)

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0; i<(n); i++)
using namespace std;
using ll = long long;

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

int main() {
    ll A, B, C, D;
    cin >> A >> B >> C >> D;

    ll lcm = C*D/gcd(C, D);
    ll cnt_a = (A-1)/C + (A-1)/D - (A-1)/lcm;
    ll cnt_b = B/C + B/D - B/lcm;

    cout << B - A + 1 + cnt_a - cnt_b << endl;
    return 0;
}