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();
        float B = sc.nextFloat();

        B += 0.001;
        B = B * 100;


        long res = (long) (A * (long) 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();
        float B = sc.nextFloat();

        B += 0.001;
        B = B * 100;


        long res = (long) (A * (long) 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();
        float B = sc.nextFloat();

        B += 0.001;
        B = B * 100;


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

        System.out.println(res);
    } main {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        float B = sc.nextFloat();

        B += 0.001;
        B = B * 100;


        long res = (long) (A * (long) 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 float B = sc.nextFloat(); B sc.nextFloat() sc.nextFloat sc B += 0.001 B 0.001 B = B * 100 B B * 100 B 100 long res = (long) (A * (long) B / 100); res (long) (A * (long) B / 100) A * (long) B A (long) 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();
        float B = sc.nextFloat();

        B += 0.001;
        B = B * 100;


        long res = (long) (A * (long) 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();
        float B = sc.nextFloat();

        B += 0.001;
        B = B * 100;


        long res = (long) (A * (long) 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();
        float B = sc.nextFloat();

        B += 0.001;
        B = B * 100;


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

        System.out.println(res);
    }
}

/*
999999999999999 9.99
 */