import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.math.BigInteger;
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;
        MyScanner in = new MyScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, MyScanner in, PrintWriter out) {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        }

    }

    static class MyScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public MyScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }

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

        public double Double() {
            return Double.parseDouble(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.math.BigInteger; BigInteger java.math 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;
        MyScanner in = new MyScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, MyScanner in, PrintWriter out) {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        }

    }

    static class MyScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public MyScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }

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

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

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyScanner in = new MyScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyScanner in = new MyScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        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 MyScanner in = new MyScanner(inputStream); in new MyScanner(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) C solver = new C(); solver new C() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class C {
        public void solve(int testNumber, MyScanner in, PrintWriter out) {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        }

    } C public void solve(int testNumber, MyScanner in, PrintWriter out) {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        } solve {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        } long A = in.Long(); A in.Long() in.Long in long B = Math.round(in.Double() * 100); B Math.round(in.Double() * 100) Math.round Math in.Double() * 100 in.Double() in.Double in 100 BigInteger a = BigInteger.valueOf(A); a BigInteger.valueOf(A) BigInteger.valueOf BigInteger A BigInteger b = BigInteger.valueOf(B); b BigInteger.valueOf(B) BigInteger.valueOf BigInteger B BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100)); ans a.multiply(b).divide(BigInteger.valueOf(100)) a.multiply(b).divide a.multiply(b) a.multiply a b BigInteger.valueOf(100) BigInteger.valueOf BigInteger 100 out.println(ans.toString()) out.println out ans.toString() ans.toString ans int testNumber testNumber MyScanner in in PrintWriter out out static class MyScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public MyScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }

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

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

    } MyScanner private BufferedReader in; in private StringTokenizer st; st public MyScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        } MyScanner {
            in = new BufferedReader(new InputStreamReader(stream));
        } in = new BufferedReader(new InputStreamReader(stream)) in new BufferedReader(new InputStreamReader(stream)) InputStream stream stream public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        } next {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        } while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            } st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            } try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                } catch (IOException e) {
                    return null;
                } IOException e {
                    return null;
                } return null; null {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } String rl = in.readLine(); rl in.readLine() in.readLine in if (rl == null) {
                        return null;
                    } rl == null rl null {
                        return null;
                    } return null; null st = new StringTokenizer(rl) st new StringTokenizer(rl) return st.nextToken(); st.nextToken() st.nextToken st public long Long() {
            return Long.parseLong(next());
        } Long {
            return Long.parseLong(next());
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public double Double() {
            return Double.parseDouble(next());
        } Double {
            return Double.parseDouble(next());
        } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyScanner in = new MyScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, MyScanner in, PrintWriter out) {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        }

    }

    static class MyScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public MyScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }

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

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

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

    static class C {
        public void solve(int testNumber, MyScanner in, PrintWriter out) {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        }

    }

    static class MyScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public MyScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }

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

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

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.math.BigInteger;
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;
        MyScanner in = new MyScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, MyScanner in, PrintWriter out) {
            long A = in.Long();
            long B = Math.round(in.Double() * 100);
            BigInteger a = BigInteger.valueOf(A);
            BigInteger b = BigInteger.valueOf(B);
            BigInteger ans = a.multiply(b).divide(BigInteger.valueOf(100));
            out.println(ans.toString());
        }

    }

    static class MyScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public MyScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }

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

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

    }
}

