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 e = lcm(c,d);
    long count = b-a+1;
    count -= b/c - (a-1)/c;
    count -= b/d - (a-1)/d;
    count += b/e - (a-1)/e;
    System.out.println(count);

  }

  private static long lcm(long a, long b){
    long temp;
    long c = a;
    c *= b;
    while((temp = a%b)!=0){
      a=b;
      b=temp;
    }
    return c/b;
  }
} import java.util.*; util.* java 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 e = lcm(c,d);
    long count = b-a+1;
    count -= b/c - (a-1)/c;
    count -= b/d - (a-1)/d;
    count += b/e - (a-1)/e;
    System.out.println(count);

  }

  private static long lcm(long a, long b){
    long temp;
    long c = a;
    c *= b;
    while((temp = a%b)!=0){
      a=b;
      b=temp;
    }
    return c/b;
  }
} 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 e = lcm(c,d);
    long count = b-a+1;
    count -= b/c - (a-1)/c;
    count -= b/d - (a-1)/d;
    count += b/e - (a-1)/e;
    System.out.println(count);

  } main {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    long b = sc.nextLong();
    long c = sc.nextLong();
    long d = sc.nextLong();
    long e = lcm(c,d);
    long count = b-a+1;
    count -= b/c - (a-1)/c;
    count -= b/d - (a-1)/d;
    count += b/e - (a-1)/e;
    System.out.println(count);

  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = sc.nextLong(); a sc.nextLong() sc.nextLong sc long b = sc.nextLong(); b sc.nextLong() sc.nextLong sc long c = sc.nextLong(); c sc.nextLong() sc.nextLong sc long d = sc.nextLong(); d sc.nextLong() sc.nextLong sc long e = lcm(c,d); e lcm(c,d) lcm c d long count = b-a+1; count b-a+1 b-a b a 1 count -= b/c - (a-1)/c count b/c - (a-1)/c b/c b c (a-1)/c (a-1) a 1 c count -= b/d - (a-1)/d count b/d - (a-1)/d b/d b d (a-1)/d (a-1) a 1 d count += b/e - (a-1)/e count b/e - (a-1)/e b/e b e (a-1)/e (a-1) a 1 e System.out.println(count) System.out.println System.out System System.out count String[] args args private static long lcm(long a, long b){
    long temp;
    long c = a;
    c *= b;
    while((temp = a%b)!=0){
      a=b;
      b=temp;
    }
    return c/b;
  } lcm {
    long temp;
    long c = a;
    c *= b;
    while((temp = a%b)!=0){
      a=b;
      b=temp;
    }
    return c/b;
  } long temp; temp long c = a; c a c *= b c b while((temp = a%b)!=0){
      a=b;
      b=temp;
    } (temp = a%b)!=0 (temp = a%b) temp a%b a b 0 {
      a=b;
      b=temp;
    } a=b a b b=temp b temp return c/b; c/b c b long a a long b b 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 e = lcm(c,d);
    long count = b-a+1;
    count -= b/c - (a-1)/c;
    count -= b/d - (a-1)/d;
    count += b/e - (a-1)/e;
    System.out.println(count);

  }

  private static long lcm(long a, long b){
    long temp;
    long c = a;
    c *= b;
    while((temp = a%b)!=0){
      a=b;
      b=temp;
    }
    return c/b;
  }
} 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 e = lcm(c,d);
    long count = b-a+1;
    count -= b/c - (a-1)/c;
    count -= b/d - (a-1)/d;
    count += b/e - (a-1)/e;
    System.out.println(count);

  }

  private static long lcm(long a, long b){
    long temp;
    long c = a;
    c *= b;
    while((temp = a%b)!=0){
      a=b;
      b=temp;
    }
    return c/b;
  }
} Main
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 e = lcm(c,d);
    long count = b-a+1;
    count -= b/c - (a-1)/c;
    count -= b/d - (a-1)/d;
    count += b/e - (a-1)/e;
    System.out.println(count);

  }

  private static long lcm(long a, long b){
    long temp;
    long c = a;
    c *= b;
    while((temp = a%b)!=0){
      a=b;
      b=temp;
    }
    return c/b;
  }
}
