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

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        }

        private long f(long l, long r, long val) {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        }

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

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

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

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

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

    }
}
 import java.io.OutputStream; OutputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.StringTokenizer; StringTokenizer java.util import java.io.IOException; IOException java.io import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.InputStream; InputStream java.io public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        }

        private long f(long l, long r, long val) {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        }

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

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

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

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

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

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out InputReader in = new InputReader(inputStream); in new InputReader(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) TaskC solver = new TaskC(); solver new TaskC() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class TaskC {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        }

        private long f(long l, long r, long val) {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        }

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

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

    } TaskC public void solve(int testNumber, InputReader in, PrintWriter out) {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        } solve {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        } long a = in.nextLong(); a in.nextLong() in.nextLong in long b = in.nextLong(); b in.nextLong() in.nextLong in long c = in.nextLong(); c in.nextLong() in.nextLong in long d = in.nextLong(); d in.nextLong() in.nextLong in long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d))); ans (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d))) (b - a + 1) b - a b a 1 (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d))) f(a, b, c) + f(a, b, d) f(a, b, c) f a b c f(a, b, d) f a b d f(a, b, lcm(c, d)) f a b lcm(c, d) lcm c d out.println(ans) out.println out ans int testNumber testNumber InputReader in in PrintWriter out out private long f(long l, long r, long val) {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        } f {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        } long u = (l + val - 1) / val; u (l + val - 1) / val (l + val - 1) l + val l val 1 val long d = r / val; d r / val r val return d - u + 1; d - u + 1 d - u d u 1 long l l long r r long val val private long gcd(long a, long b) {
            if (b == 0)
                return a;
            else
                return gcd(b, a % b);
        } gcd {
            if (b == 0)
                return a;
            else
                return gcd(b, a % b);
        } if (b == 0)
                return a;
            else
                return gcd(b, a % b); b == 0 b 0 return a; a return gcd(b, a % b); gcd(b, a % b) gcd b a % b a b long a a long b b private long lcm(long a, long b) {
            return a / gcd(a, b) * b;
        } lcm {
            return a / gcd(a, b) * b;
        } return a / gcd(a, b) * b; a / gcd(a, b) * b a / gcd(a, b) a gcd(a, b) gcd a b b long a a long b b static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

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

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

    } InputReader public BufferedReader reader; reader public StringTokenizer tokenizer; tokenizer public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        } InputReader {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        } reader = new BufferedReader(new InputStreamReader(stream), 32768) reader new BufferedReader(new InputStreamReader(stream), 32768) tokenizer = null tokenizer null InputStream stream stream public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        } next {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        } while (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 long nextLong() {
            return Long.parseLong(next());
        } nextLong {
            return Long.parseLong(next());
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        }

        private long f(long l, long r, long val) {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        }

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

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

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

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

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

    }
} public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        }

        private long f(long l, long r, long val) {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        }

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

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

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

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

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

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long a = in.nextLong();
            long b = in.nextLong();
            long c = in.nextLong();
            long d = in.nextLong();
            long ans = (b - a + 1) - (f(a, b, c) + f(a, b, d) - f(a, b, lcm(c, d)));
            out.println(ans);
        }

        private long f(long l, long r, long val) {
            long u = (l + val - 1) / val;
            long d = r / val;
            return d - u + 1;
        }

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

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

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

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

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

    }
}

