import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * 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;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Multiplication3 solver = new Multiplication3();
        solver.solve(1, in, out);
        out.close();
    }

    static class Multiplication3 {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        }

    }
}
 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.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Multiplication3 solver = new Multiplication3();
        solver.solve(1, in, out);
        out.close();
    }

    static class Multiplication3 {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        }

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Multiplication3 solver = new Multiplication3();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Multiplication3 solver = new Multiplication3();
        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 Scanner in = new Scanner(inputStream); in new Scanner(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) Multiplication3 solver = new Multiplication3(); solver new Multiplication3() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class Multiplication3 {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        }

    } Multiplication3 public void solve(int testNumber, Scanner in, PrintWriter out) {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        } solve {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        } String[] inputs = in.nextLine().split(" "); inputs in.nextLine().split(" ") in.nextLine().split in.nextLine() in.nextLine in " " long a = Long.parseLong(inputs[0]); a Long.parseLong(inputs[0]) Long.parseLong Long inputs[0] inputs 0 long b = Long.parseLong(inputs[1].replaceAll("\\.", "")); b Long.parseLong(inputs[1].replaceAll("\\.", "")) Long.parseLong Long inputs[1].replaceAll("\\.", "") inputs[1].replaceAll inputs[1] inputs 1 "\\." "" out.append(String.valueOf(a * b / 100)) out.append out String.valueOf(a * b / 100) String.valueOf String a * b / 100 a * b a b 100 int testNumber testNumber Scanner in in PrintWriter out out public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Multiplication3 solver = new Multiplication3();
        solver.solve(1, in, out);
        out.close();
    }

    static class Multiplication3 {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        }

    }
} public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Multiplication3 solver = new Multiplication3();
        solver.solve(1, in, out);
        out.close();
    }

    static class Multiplication3 {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * 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;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Multiplication3 solver = new Multiplication3();
        solver.solve(1, in, out);
        out.close();
    }

    static class Multiplication3 {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            String[] inputs = in.nextLine().split(" ");
            long a = Long.parseLong(inputs[0]);
            long b = Long.parseLong(inputs[1].replaceAll("\\.", ""));

            out.append(String.valueOf(a * b / 100));


        }

    }
}

