import java.io.*;
import java.util.*;
public class Main
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	}
} import java.io.*; io.* java import java.util.*; util.* java public class Main
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	}
} Main public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st = new StringTokenizer(br.readLine()); st new StringTokenizer(br.readLine()) Long a = Long.parseLong(st.nextToken()); a Long.parseLong(st.nextToken()) Long.parseLong Long st.nextToken() st.nextToken st String b = (st.nextToken()); b (st.nextToken()) st.nextToken st long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1)); b1 Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1)) Long.parseLong Long b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1) b.substring(0,b.indexOf('.')) b.substring b 0 b.indexOf('.') b.indexOf b '.' b.substring(b.indexOf('.')+1) b.substring b b.indexOf('.')+1 b.indexOf('.') b.indexOf b '.' 1 System.out.println((a*b1)/100) System.out.println System.out System System.out (a*b1)/100 (a*b1) a b1 100 String args[] args public class Main
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	}
} public class Main
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	}
} Main
import java.io.*;
import java.util.*;
public class Main
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	}
}