import java.util.Scanner;

public class Main {

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

        final long A = sc.nextLong();
        final long B = sc.nextLong();
        final long C = sc.nextLong();
        final long D = sc.nextLong();
        final long L = lcm(C, D);
        System.out.println((B - B / C - B / D + B / L) - ((A-1) - (A-1) / C - (A-1) / D + (A-1) / L));
    }

    private static long lcm(long a, long b) {
        return a * b / gcd(a, b);
    }

    private static long gcd(long a, long b) {
        if (b == 0) return a;
        return gcd(b, a % b);
    }
}

/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