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

public class Main {
	public static void main(String[] args) {
		FastScanner sc = new FastScanner(System.in);
		long a = sc.nextLong(), b = sc.nextLong(),c = sc.nextLong(), d = sc.nextLong();
		long ans = b/c - a/c;
		if(a%c == 0) {
			ans++;
		}
		ans += b/d - a/d;
		if(a%d == 0) {
			ans++;
		}
		long cd = lcm(c,d);
		ans -= b/cd - a/cd;
		if(a%cd == 0) {
			ans--;
		}
		System.out.println(b - a + 1 - ans);
	}

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

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

	static class FastScanner {
		private BufferedReader reader = null;
	    private StringTokenizer tokenizer = null;
	    public FastScanner(InputStream in) {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    }

	    public String next() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    }

	    public String nextLine() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    }

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

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

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

	    public int[] nextIntArray(int n) {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    }

	    public long[] nextLongArray(int n) {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    }
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream 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) {
		FastScanner sc = new FastScanner(System.in);
		long a = sc.nextLong(), b = sc.nextLong(),c = sc.nextLong(), d = sc.nextLong();
		long ans = b/c - a/c;
		if(a%c == 0) {
			ans++;
		}
		ans += b/d - a/d;
		if(a%d == 0) {
			ans++;
		}
		long cd = lcm(c,d);
		ans -= b/cd - a/cd;
		if(a%cd == 0) {
			ans--;
		}
		System.out.println(b - a + 1 - ans);
	}

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

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

	static class FastScanner {
		private BufferedReader reader = null;
	    private StringTokenizer tokenizer = null;
	    public FastScanner(InputStream in) {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    }

	    public String next() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    }

	    public String nextLine() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    }

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

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

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

	    public int[] nextIntArray(int n) {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    }

	    public long[] nextLongArray(int n) {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    }
	}
} Main public static void main(String[] args) {
		FastScanner sc = new FastScanner(System.in);
		long a = sc.nextLong(), b = sc.nextLong(),c = sc.nextLong(), d = sc.nextLong();
		long ans = b/c - a/c;
		if(a%c == 0) {
			ans++;
		}
		ans += b/d - a/d;
		if(a%d == 0) {
			ans++;
		}
		long cd = lcm(c,d);
		ans -= b/cd - a/cd;
		if(a%cd == 0) {
			ans--;
		}
		System.out.println(b - a + 1 - ans);
	} main {
		FastScanner sc = new FastScanner(System.in);
		long a = sc.nextLong(), b = sc.nextLong(),c = sc.nextLong(), d = sc.nextLong();
		long ans = b/c - a/c;
		if(a%c == 0) {
			ans++;
		}
		ans += b/d - a/d;
		if(a%d == 0) {
			ans++;
		}
		long cd = lcm(c,d);
		ans -= b/cd - a/cd;
		if(a%cd == 0) {
			ans--;
		}
		System.out.println(b - a + 1 - ans);
	} FastScanner sc = new FastScanner(System.in); sc new FastScanner(System.in) long a = sc.nextLong() a sc.nextLong() sc.nextLong sc b = sc.nextLong() b sc.nextLong() sc.nextLong sc c = sc.nextLong() c sc.nextLong() sc.nextLong sc d = sc.nextLong(); d sc.nextLong() sc.nextLong sc long ans = b/c - a/c; ans b/c - a/c b/c b c a/c a c if(a%c == 0) {
			ans++;
		} a%c == 0 a%c a c 0 {
			ans++;
		} ans++ ans ans += b/d - a/d ans b/d - a/d b/d b d a/d a d if(a%d == 0) {
			ans++;
		} a%d == 0 a%d a d 0 {
			ans++;
		} ans++ ans long cd = lcm(c,d); cd lcm(c,d) lcm c d ans -= b/cd - a/cd ans b/cd - a/cd b/cd b cd a/cd a cd if(a%cd == 0) {
			ans--;
		} a%cd == 0 a%cd a cd 0 {
			ans--;
		} ans-- ans System.out.println(b - a + 1 - ans) System.out.println System.out System System.out b - a + 1 - ans b - a + 1 b - a b a 1 ans String[] args args static long gcd(long a, long b) {
		if(a%b == 0)return b;
		else return gcd(b, a%b);
	} gcd {
		if(a%b == 0)return b;
		else return gcd(b, a%b);
	} if(a%b == 0)return b;
		else return gcd(b, a%b); a%b == 0 a%b a b 0 return b; b return gcd(b, a%b); gcd(b, a%b) gcd b a%b a b long a a long b b static long lcm(long a, long b) {
		return a * b / gcd(a,b);
	} lcm {
		return a * b / gcd(a,b);
	} return a * b / gcd(a,b); a * b / gcd(a,b) a * b a b gcd(a,b) gcd a b long a a long b b static class FastScanner {
		private BufferedReader reader = null;
	    private StringTokenizer tokenizer = null;
	    public FastScanner(InputStream in) {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    }

	    public String next() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    }

	    public String nextLine() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    }

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

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

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

	    public int[] nextIntArray(int n) {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    }

	    public long[] nextLongArray(int n) {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    }
	} FastScanner private BufferedReader reader = null; reader null private StringTokenizer tokenizer = null; tokenizer null public FastScanner(InputStream in) {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    } FastScanner {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    } reader = new BufferedReader(new InputStreamReader(in)) reader new BufferedReader(new InputStreamReader(in)) tokenizer = null tokenizer null InputStream in in public String next() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    } next {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    } if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        } tokenizer == null || !tokenizer.hasMoreTokens() tokenizer == null tokenizer null !tokenizer.hasMoreTokens() tokenizer.hasMoreTokens() tokenizer.hasMoreTokens tokenizer {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        } try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            } IOException e {
	                throw new RuntimeException(e);
	            } throw new RuntimeException(e); new RuntimeException(e) {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } tokenizer = new StringTokenizer(reader.readLine()) tokenizer new StringTokenizer(reader.readLine()) return tokenizer.nextToken(); tokenizer.nextToken() tokenizer.nextToken tokenizer public String nextLine() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    } nextLine {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    } if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        } tokenizer == null || !tokenizer.hasMoreTokens() tokenizer == null tokenizer null !tokenizer.hasMoreTokens() tokenizer.hasMoreTokens() tokenizer.hasMoreTokens tokenizer {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        } try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            } IOException e {
	                throw new RuntimeException(e);
	            } throw new RuntimeException(e); new RuntimeException(e) {
	                return reader.readLine();
	            } return reader.readLine(); reader.readLine() reader.readLine reader return tokenizer.nextToken("\n"); tokenizer.nextToken("\n") tokenizer.nextToken tokenizer "\n" public long nextLong() {
	        return Long.parseLong(next());
	    } nextLong {
	        return Long.parseLong(next());
	    } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public int nextInt() {
	        return Integer.parseInt(next());
	    } nextInt {
	        return Integer.parseInt(next());
	    } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next public double nextDouble() {
	         return Double.parseDouble(next());
	     } nextDouble {
	         return Double.parseDouble(next());
	     } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next public int[] nextIntArray(int n) {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    } nextIntArray {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    } int[] a = new int[n]; a new int[n] n for (int i = 0; i < n; i++)
	            a[i] = nextInt(); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = nextInt(); a[i] = nextInt() a[i] a i nextInt() nextInt return a; a int n n public long[] nextLongArray(int n) {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    } nextLongArray {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    } long[] a = new long[n]; a new long[n] n for (int i = 0; i < n; i++)
	            a[i] = nextLong(); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = nextLong(); a[i] = nextLong() a[i] a i nextLong() nextLong return a; a int n n public class Main {
	public static void main(String[] args) {
		FastScanner sc = new FastScanner(System.in);
		long a = sc.nextLong(), b = sc.nextLong(),c = sc.nextLong(), d = sc.nextLong();
		long ans = b/c - a/c;
		if(a%c == 0) {
			ans++;
		}
		ans += b/d - a/d;
		if(a%d == 0) {
			ans++;
		}
		long cd = lcm(c,d);
		ans -= b/cd - a/cd;
		if(a%cd == 0) {
			ans--;
		}
		System.out.println(b - a + 1 - ans);
	}

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

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

	static class FastScanner {
		private BufferedReader reader = null;
	    private StringTokenizer tokenizer = null;
	    public FastScanner(InputStream in) {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    }

	    public String next() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    }

	    public String nextLine() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    }

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

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

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

	    public int[] nextIntArray(int n) {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    }

	    public long[] nextLongArray(int n) {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    }
	}
} public class Main {
	public static void main(String[] args) {
		FastScanner sc = new FastScanner(System.in);
		long a = sc.nextLong(), b = sc.nextLong(),c = sc.nextLong(), d = sc.nextLong();
		long ans = b/c - a/c;
		if(a%c == 0) {
			ans++;
		}
		ans += b/d - a/d;
		if(a%d == 0) {
			ans++;
		}
		long cd = lcm(c,d);
		ans -= b/cd - a/cd;
		if(a%cd == 0) {
			ans--;
		}
		System.out.println(b - a + 1 - ans);
	}

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

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

	static class FastScanner {
		private BufferedReader reader = null;
	    private StringTokenizer tokenizer = null;
	    public FastScanner(InputStream in) {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    }

	    public String next() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    }

	    public String nextLine() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    }

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

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

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

	    public int[] nextIntArray(int n) {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    }

	    public long[] nextLongArray(int n) {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    }
	}
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
	public static void main(String[] args) {
		FastScanner sc = new FastScanner(System.in);
		long a = sc.nextLong(), b = sc.nextLong(),c = sc.nextLong(), d = sc.nextLong();
		long ans = b/c - a/c;
		if(a%c == 0) {
			ans++;
		}
		ans += b/d - a/d;
		if(a%d == 0) {
			ans++;
		}
		long cd = lcm(c,d);
		ans -= b/cd - a/cd;
		if(a%cd == 0) {
			ans--;
		}
		System.out.println(b - a + 1 - ans);
	}

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

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

	static class FastScanner {
		private BufferedReader reader = null;
	    private StringTokenizer tokenizer = null;
	    public FastScanner(InputStream in) {
	        reader = new BufferedReader(new InputStreamReader(in));
	        tokenizer = null;
	    }

	    public String next() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                tokenizer = new StringTokenizer(reader.readLine());
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }
	        return tokenizer.nextToken();
	    }

	    public String nextLine() {
	        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	                return reader.readLine();
	            } catch (IOException e) {
	                throw new RuntimeException(e);
	            }
	        }

	        return tokenizer.nextToken("\n");
	    }

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

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

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

	    public int[] nextIntArray(int n) {
	        int[] a = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    }

	    public long[] nextLongArray(int n) {
	        long[] a = new long[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextLong();
	        return a;
	    }
	}
}
