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

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String b = sc.next();

        long B = 0;
        B += b.charAt(0) - '0';
        B *= 10;
        B += b.charAt(2) - '0';
        B *= 10;
        B += b.charAt(3) - '0';


        long res = (long) (A * B / 100);
        //long res = (A * (long)(B * 100)) / 100;

        System.out.println(res);
    }
}

/*
999999999999999 9.99
 */ import java.util.*; util.* java import java.math.*; math.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String b = sc.next();

        long B = 0;
        B += b.charAt(0) - '0';
        B *= 10;
        B += b.charAt(2) - '0';
        B *= 10;
        B += b.charAt(3) - '0';


        long res = (long) (A * B / 100);
        //long res = (A * (long)(B * 100)) / 100;

        System.out.println(res);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String b = sc.next();

        long B = 0;
        B += b.charAt(0) - '0';
        B *= 10;
        B += b.charAt(2) - '0';
        B *= 10;
        B += b.charAt(3) - '0';


        long res = (long) (A * B / 100);
        //long res = (A * (long)(B * 100)) / 100;

        System.out.println(res);
    } main {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String b = sc.next();

        long B = 0;
        B += b.charAt(0) - '0';
        B *= 10;
        B += b.charAt(2) - '0';
        B *= 10;
        B += b.charAt(3) - '0';


        long res = (long) (A * B / 100);
        //long res = (A * (long)(B * 100)) / 100;

        System.out.println(res);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc String b = sc.next(); b sc.next() sc.next sc long B = 0; B 0 B += b.charAt(0) - '0' B b.charAt(0) - '0' b.charAt(0) b.charAt b 0 '0' B *= 10 B 10 B += b.charAt(2) - '0' B b.charAt(2) - '0' b.charAt(2) b.charAt b 2 '0' B *= 10 B 10 B += b.charAt(3) - '0' B b.charAt(3) - '0' b.charAt(3) b.charAt b 3 '0' long res = (long) (A * B / 100); res (long) (A * B / 100) A * B A B 100 System.out.println(res) System.out.println System.out System System.out res String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String b = sc.next();

        long B = 0;
        B += b.charAt(0) - '0';
        B *= 10;
        B += b.charAt(2) - '0';
        B *= 10;
        B += b.charAt(3) - '0';


        long res = (long) (A * B / 100);
        //long res = (A * (long)(B * 100)) / 100;

        System.out.println(res);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String b = sc.next();

        long B = 0;
        B += b.charAt(0) - '0';
        B *= 10;
        B += b.charAt(2) - '0';
        B *= 10;
        B += b.charAt(3) - '0';


        long res = (long) (A * B / 100);
        //long res = (A * (long)(B * 100)) / 100;

        System.out.println(res);
    }
} Main
import java.util.*;
import java.math.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String b = sc.next();

        long B = 0;
        B += b.charAt(0) - '0';
        B *= 10;
        B += b.charAt(2) - '0';
        B *= 10;
        B += b.charAt(3) - '0';


        long res = (long) (A * B / 100);
        //long res = (A * (long)(B * 100)) / 100;

        System.out.println(res);
    }
}

/*
999999999999999 9.99
 */