
import java.util.*;
 interface aisatu{
	final String str="こんにちは";
	void mesod();
}

public class Main {
	static public void main(String args[]){
		Scanner sc=new Scanner(System.in);
		
		long a=sc.nextLong();
		int b=(int)(sc.nextDouble()*100+0.01);
		
		System.out.print((a*b)/100);
	}

}
 import java.util.*; util.* java interface aisatu{
	final String str="こんにちは";
	void mesod();
} aisatu final String str="こんにちは"; str "こんにちは" void mesod(); mesod public class Main {
	static public void main(String args[]){
		Scanner sc=new Scanner(System.in);
		
		long a=sc.nextLong();
		int b=(int)(sc.nextDouble()*100+0.01);
		
		System.out.print((a*b)/100);
	}

} Main static public void main(String args[]){
		Scanner sc=new Scanner(System.in);
		
		long a=sc.nextLong();
		int b=(int)(sc.nextDouble()*100+0.01);
		
		System.out.print((a*b)/100);
	} main {
		Scanner sc=new Scanner(System.in);
		
		long a=sc.nextLong();
		int b=(int)(sc.nextDouble()*100+0.01);
		
		System.out.print((a*b)/100);
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) long a=sc.nextLong(); a sc.nextLong() sc.nextLong sc int b=(int)(sc.nextDouble()*100+0.01); b (int)(sc.nextDouble()*100+0.01) sc.nextDouble()*100 sc.nextDouble() sc.nextDouble sc 100 0.01 System.out.print((a*b)/100) System.out.print System.out System System.out (a*b)/100 (a*b) a b 100 String args[] args public class Main {
	static public void main(String args[]){
		Scanner sc=new Scanner(System.in);
		
		long a=sc.nextLong();
		int b=(int)(sc.nextDouble()*100+0.01);
		
		System.out.print((a*b)/100);
	}

} public class Main {
	static public void main(String args[]){
		Scanner sc=new Scanner(System.in);
		
		long a=sc.nextLong();
		int b=(int)(sc.nextDouble()*100+0.01);
		
		System.out.print((a*b)/100);
	}

} Main

import java.util.*;
 interface aisatu{
	final String str="こんにちは";
	void mesod();
}

public class Main {
	static public void main(String args[]){
		Scanner sc=new Scanner(System.in);
		
		long a=sc.nextLong();
		int b=(int)(sc.nextDouble()*100+0.01);
		
		System.out.print((a*b)/100);
	}

}

