import java.util.Scanner;
class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong() - 1;
    long b = sc.nextLong();
    int c = sc.nextInt();
    int d = sc.nextInt();
    long x = a - (a/c) - (a/d) +(a / lcm(c,d));
    long y = b - (b/c) - (b/d) + (b/lcm(c,d));
    System.out.println(y - x);
  }
  public static long lcm(int a, int b){
    return (long)a * b / gcd(a , b);
  }
  public static int gcd(int a, int b){
   if(a % b == 0){
     return b;
   }
    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