
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
  public static void main(String[] args) {
	  FastReader sc = new FastReader();
	  long a = sc.nextLong();
	  long b = sc.nextLong();
	  long c = sc.nextLong();
	  long d = sc.nextLong();
	  
	  long lcm = (c*d)/ gcd(d, c);
	  
	  long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm));
	  
	  System.out.println(res);
  }
 
  private static long gcd(long m, long n) {
	  if (m < n) {
		  return gcd(n, m);
	  }
	  
	  if (n == 0) {
		  return m;
	  }
	  
	  return gcd(n, m % n);
  }
 
  static class FastReader {
    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
      br = new BufferedReader(new InputStreamReader(System.in));
    }
  
    String next() { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    }

    int nextInt() {
      return Integer.parseInt(next());
    }

    long nextLong() {
      return Long.parseLong(next());
    }

    double nextDouble() { 
      return Double.parseDouble(next());
    }

    String nextLine() {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      }
  }
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.StringTokenizer; StringTokenizer java.util public class Main {
  public static void main(String[] args) {
	  FastReader sc = new FastReader();
	  long a = sc.nextLong();
	  long b = sc.nextLong();
	  long c = sc.nextLong();
	  long d = sc.nextLong();
	  
	  long lcm = (c*d)/ gcd(d, c);
	  
	  long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm));
	  
	  System.out.println(res);
  }
 
  private static long gcd(long m, long n) {
	  if (m < n) {
		  return gcd(n, m);
	  }
	  
	  if (n == 0) {
		  return m;
	  }
	  
	  return gcd(n, m % n);
  }
 
  static class FastReader {
    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
      br = new BufferedReader(new InputStreamReader(System.in));
    }
  
    String next() { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    }

    int nextInt() {
      return Integer.parseInt(next());
    }

    long nextLong() {
      return Long.parseLong(next());
    }

    double nextDouble() { 
      return Double.parseDouble(next());
    }

    String nextLine() {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      }
  }
} Main public static void main(String[] args) {
	  FastReader sc = new FastReader();
	  long a = sc.nextLong();
	  long b = sc.nextLong();
	  long c = sc.nextLong();
	  long d = sc.nextLong();
	  
	  long lcm = (c*d)/ gcd(d, c);
	  
	  long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm));
	  
	  System.out.println(res);
  } main {
	  FastReader sc = new FastReader();
	  long a = sc.nextLong();
	  long b = sc.nextLong();
	  long c = sc.nextLong();
	  long d = sc.nextLong();
	  
	  long lcm = (c*d)/ gcd(d, c);
	  
	  long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm));
	  
	  System.out.println(res);
  } FastReader sc = new FastReader(); sc new FastReader() 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 lcm = (c*d)/ gcd(d, c); lcm (c*d)/ gcd(d, c) (c*d) c d gcd(d, c) gcd d c long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm)); res (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm)) (b - (b/c + b/d - b/lcm)) b (b/c + b/d - b/lcm) b/c + b/d b/c b c b/d b d b/lcm b lcm ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm)) (a-1) a 1 ((a-1)/c + (a-1)/d - (a-1)/lcm) (a-1)/c + (a-1)/d (a-1)/c (a-1) a 1 c (a-1)/d (a-1) a 1 d (a-1)/lcm (a-1) a 1 lcm System.out.println(res) System.out.println System.out System System.out res String[] args args private static long gcd(long m, long n) {
	  if (m < n) {
		  return gcd(n, m);
	  }
	  
	  if (n == 0) {
		  return m;
	  }
	  
	  return gcd(n, m % n);
  } gcd {
	  if (m < n) {
		  return gcd(n, m);
	  }
	  
	  if (n == 0) {
		  return m;
	  }
	  
	  return gcd(n, m % n);
  } if (m < n) {
		  return gcd(n, m);
	  } m < n m n {
		  return gcd(n, m);
	  } return gcd(n, m); gcd(n, m) gcd n m if (n == 0) {
		  return m;
	  } n == 0 n 0 {
		  return m;
	  } return m; m return gcd(n, m % n); gcd(n, m % n) gcd n m % n m n long m m long n n static class FastReader {
    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
      br = new BufferedReader(new InputStreamReader(System.in));
    }
  
    String next() { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    }

    int nextInt() {
      return Integer.parseInt(next());
    }

    long nextLong() {
      return Long.parseLong(next());
    }

    double nextDouble() { 
      return Double.parseDouble(next());
    }

    String nextLine() {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      }
  } FastReader BufferedReader br; br StringTokenizer st; st public FastReader() {
      br = new BufferedReader(new InputStreamReader(System.in));
    } FastReader {
      br = new BufferedReader(new InputStreamReader(System.in));
    } br = new BufferedReader(new InputStreamReader(System.in)) br new BufferedReader(new InputStreamReader(System.in)) String next() { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    } next { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    } while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      } try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        } catch (IOException  e) {
          e.printStackTrace();
        } IOException  e {
          e.printStackTrace();
        } e.printStackTrace() e.printStackTrace e {
          st = new StringTokenizer(br.readLine());
        } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() {
      return Integer.parseInt(next());
    } nextInt {
      return Integer.parseInt(next());
    } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nextLong() {
      return Long.parseLong(next());
    } nextLong {
      return Long.parseLong(next());
    } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble() { 
      return Double.parseDouble(next());
    } nextDouble { 
      return Double.parseDouble(next());
    } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine() {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      } nextLine {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      } String str = ""; str "" try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } IOException e {
            e.printStackTrace();
        } e.printStackTrace() e.printStackTrace e {
            str = br.readLine();
        } str = br.readLine() str br.readLine() br.readLine br return str; str public class Main {
  public static void main(String[] args) {
	  FastReader sc = new FastReader();
	  long a = sc.nextLong();
	  long b = sc.nextLong();
	  long c = sc.nextLong();
	  long d = sc.nextLong();
	  
	  long lcm = (c*d)/ gcd(d, c);
	  
	  long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm));
	  
	  System.out.println(res);
  }
 
  private static long gcd(long m, long n) {
	  if (m < n) {
		  return gcd(n, m);
	  }
	  
	  if (n == 0) {
		  return m;
	  }
	  
	  return gcd(n, m % n);
  }
 
  static class FastReader {
    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
      br = new BufferedReader(new InputStreamReader(System.in));
    }
  
    String next() { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    }

    int nextInt() {
      return Integer.parseInt(next());
    }

    long nextLong() {
      return Long.parseLong(next());
    }

    double nextDouble() { 
      return Double.parseDouble(next());
    }

    String nextLine() {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      }
  }
} public class Main {
  public static void main(String[] args) {
	  FastReader sc = new FastReader();
	  long a = sc.nextLong();
	  long b = sc.nextLong();
	  long c = sc.nextLong();
	  long d = sc.nextLong();
	  
	  long lcm = (c*d)/ gcd(d, c);
	  
	  long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm));
	  
	  System.out.println(res);
  }
 
  private static long gcd(long m, long n) {
	  if (m < n) {
		  return gcd(n, m);
	  }
	  
	  if (n == 0) {
		  return m;
	  }
	  
	  return gcd(n, m % n);
  }
 
  static class FastReader {
    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
      br = new BufferedReader(new InputStreamReader(System.in));
    }
  
    String next() { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    }

    int nextInt() {
      return Integer.parseInt(next());
    }

    long nextLong() {
      return Long.parseLong(next());
    }

    double nextDouble() { 
      return Double.parseDouble(next());
    }

    String nextLine() {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      }
  }
} Main

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
  public static void main(String[] args) {
	  FastReader sc = new FastReader();
	  long a = sc.nextLong();
	  long b = sc.nextLong();
	  long c = sc.nextLong();
	  long d = sc.nextLong();
	  
	  long lcm = (c*d)/ gcd(d, c);
	  
	  long res = (b - (b/c + b/d - b/lcm)) - ((a-1) - ((a-1)/c + (a-1)/d - (a-1)/lcm));
	  
	  System.out.println(res);
  }
 
  private static long gcd(long m, long n) {
	  if (m < n) {
		  return gcd(n, m);
	  }
	  
	  if (n == 0) {
		  return m;
	  }
	  
	  return gcd(n, m % n);
  }
 
  static class FastReader {
    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
      br = new BufferedReader(new InputStreamReader(System.in));
    }
  
    String next() { 
      while (st == null || !st.hasMoreElements()) {
        try {
          st = new StringTokenizer(br.readLine());
        } catch (IOException  e) {
          e.printStackTrace();
        }
      }
      return st.nextToken();
    }

    int nextInt() {
      return Integer.parseInt(next());
    }

    long nextLong() {
      return Long.parseLong(next());
    }

    double nextDouble() { 
      return Double.parseDouble(next());
    }

    String nextLine() {
      String str = "";
        try{
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
      }
  }
}
