import java.math.BigDecimal;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    }
} import java.math.BigDecimal; BigDecimal java.math import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    }
} Main public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    } main {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) BigDecimal a = new BigDecimal(scanner.nextLong()); a new BigDecimal(scanner.nextLong()) String tmp = scanner.next().replace(".",""); tmp scanner.next().replace(".","") scanner.next().replace scanner.next() scanner.next scanner "." "" BigDecimal b = new BigDecimal(Long.valueOf(tmp)); b new BigDecimal(Long.valueOf(tmp)) System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue()) System.out.println System.out System System.out a.multiply(b).divide(new BigDecimal(100)).longValue() a.multiply(b).divide(new BigDecimal(100)).longValue a.multiply(b).divide(new BigDecimal(100)) a.multiply(b).divide a.multiply(b) a.multiply a b new BigDecimal(100) String[] args args public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    }
} public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    }
} Main
import java.math.BigDecimal;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    }
}