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;

long long ndivide(long long A, long long B, long long C){
    long long upper = B / C;
    long long lower = A / C;
    if(A % C == 0){
        // cout << upper - lower + 1 << endl;
        return upper - lower + 1;
    }
    else{
        // cout << upper - lower << endl;
        return upper - lower;
    }
}

long long gcd(long long A, long long B){
    if(A < B){
        long long tmp = A;
        A = B;
        B = tmp;
    }
    if(B == 0) return A;
    return gcd(B, A%B);
}

int main(){
    long long A, B;
    long long C, D;

    cin >> A >> B >> C >> D;

    cout << (B-A+1) - (ndivide(A, B, C)+ndivide(A, B, D)-ndivide(A, B, C*D/gcd(C, D))) << "\n";
    return 0;
}