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 xa = a-1-((a-1)/c+(a-1)/d-(a-1)/lcm(c,d));
      long xb = b-(b/c+b/d-b/lcm(c,d));
      System.out.println(xb-xa);
    }
    public static long lcm(long x,long y){
      return x*y/gcd(x,y);
    }
    public static long gcd(long x,long y){
      if(x < y)return gcd(y,x);
      if(y==0)return x;
      return gcd(y,x%y);
    }
}
/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