import java.util.*;

public class Main{
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);

        long a = sc.nextLong();
        long b = sc.nextLong();
        long c = sc.nextLong();
        long d = sc.nextLong();

        long count = b - a + 1;

        count -= counter(a, b, c);
        count -= counter(a, b, d);
        count += counter(a, b, lcm(c, d));

        System.out.println(count);
        sc.close();
    }

    static long gcd(long m, long n) {
        if (m < n)
            return gcd(n, m);
        if(n == 0)
            return m;
        return gcd(n, m%n);
    }

    static long lcm(long m, long n){
        return ((m*n) / gcd(m, n));
    }

    static long counter(long a, long b, long n){
        if(a%n == 0)
            return ((b/n) - (a/n) + 1);
        else
            return ((b/n) - (a/n));
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz