import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;

public class Main{
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	}
} import java.math.BigDecimal; BigDecimal java.math import java.math.BigInteger; BigInteger java.math import java.util.ArrayList; ArrayList java.util import java.util.HashMap; HashMap java.util import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	}
} Main public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	} main {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) BigInteger myBI = new BigInteger(sc.next()); myBI new BigInteger(sc.next()) double a = sc.nextDouble(); a sc.nextDouble() sc.nextDouble sc BigDecimal bd = new BigDecimal(myBI); bd new BigDecimal(myBI) BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger(); doubleWithStringValue bd.multiply(BigDecimal.valueOf(a)).toBigInteger() bd.multiply(BigDecimal.valueOf(a)).toBigInteger bd.multiply(BigDecimal.valueOf(a)) bd.multiply bd BigDecimal.valueOf(a) BigDecimal.valueOf BigDecimal a long result=doubleWithStringValue.longValue(); result doubleWithStringValue.longValue() doubleWithStringValue.longValue doubleWithStringValue System.out.println(result) System.out.println System.out System System.out result String args[] args public class Main{
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	}
} public class Main{
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	}
} Main
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;

public class Main{
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	}
}
