	import java.util.*;
	import java.util.Map.Entry;
	 
	 
	 class Main {
		 static int mod =  (int) (Math.pow(10,9)+7);
//		 static int mod =  (int) 998244353;
		 public static void main(String[] args) {
	    	
	        Scanner sc = new Scanner(System.in);

	        long A = sc.nextLong();
	        double B = sc.nextDouble();
	        long C = Math.round(B*100);
	        long ans=A*C/100;
	        System.out.println(ans);
	    }
	} import java.util.*; util.* java import java.util.Map.Entry; Entry java.util.Map class Main {
		 static int mod =  (int) (Math.pow(10,9)+7);
//		 static int mod =  (int) 998244353;
		 public static void main(String[] args) {
	    	
	        Scanner sc = new Scanner(System.in);

	        long A = sc.nextLong();
	        double B = sc.nextDouble();
	        long C = Math.round(B*100);
	        long ans=A*C/100;
	        System.out.println(ans);
	    }
	} Main static int mod =  (int) (Math.pow(10,9)+7); mod (int) (Math.pow(10,9)+7) Math.pow(10,9) Math.pow Math 10 9 7 //		 static int mod =  (int) 998244353;
		 public static void main(String[] args) {
	    	
	        Scanner sc = new Scanner(System.in);

	        long A = sc.nextLong();
	        double B = sc.nextDouble();
	        long C = Math.round(B*100);
	        long ans=A*C/100;
	        System.out.println(ans);
	    } main {
	    	
	        Scanner sc = new Scanner(System.in);

	        long A = sc.nextLong();
	        double B = sc.nextDouble();
	        long C = Math.round(B*100);
	        long ans=A*C/100;
	        System.out.println(ans);
	    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc double B = sc.nextDouble(); B sc.nextDouble() sc.nextDouble sc long C = Math.round(B*100); C Math.round(B*100) Math.round Math B*100 B 100 long ans=A*C/100; ans A*C/100 A*C A C 100 System.out.println(ans) System.out.println System.out System System.out ans String[] args args
	import java.util.*;
	import java.util.Map.Entry;
	 
	 
	 class Main {
		 static int mod =  (int) (Math.pow(10,9)+7);
//		 static int mod =  (int) 998244353;
		 public static void main(String[] args) {
	    	
	        Scanner sc = new Scanner(System.in);

	        long A = sc.nextLong();
	        double B = sc.nextDouble();
	        long C = Math.round(B*100);
	        long ans=A*C/100;
	        System.out.println(ans);
	    }
	}