import java.util.Scanner;
public class Main{
    public static long gcd(long a, long b){
        if(a < b) {
            long tmp = a;
            a = b;
            b = tmp;
        }
        if(b==0) return a;
        return gcd(b,a%b);
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        long a = sc.nextLong() - 1;
        long b = sc.nextLong();
        long c = sc.nextLong();
        long d = sc.nextLong();

        long lcm = c * d / gcd(c,d);
        long n = b - (b/c) - (b/d) + (b/lcm);
        long m = a - (a/c) - (a/d) + (a/lcm);

        System.out.println(n-m);
    }
}

/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