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

public class Main {

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

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/100;

    System.out.println(ans);
  }

} import java.util.*; util.* java import java.math.*; math.* java import java.lang.*; lang.* java public class Main {

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

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/100;

    System.out.println(ans);
  }

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

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/100;

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

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/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 String b = sc.next(); b sc.next() sc.next sc char[] c = b.toCharArray(); c b.toCharArray() b.toCharArray b long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0'); k (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0') (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0') (c[0]-'0')*100 (c[0]-'0') c[0] c 0 '0' 100 (c[2]-'0')*10 (c[2]-'0') c[2] c 2 '0' 10 (c[3]-'0') c[3] c 3 '0' long ans = a*k/100; ans a*k/100 a*k a k 100 System.out.println(ans) System.out.println System.out System System.out ans 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();

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/100;

    System.out.println(ans);
  }

} public class Main {

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

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/100;

    System.out.println(ans);
  }

} Main
import java.util.*;
import java.math.*;
import java.lang.*;

public class Main {

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

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/100;

    System.out.println(ans);
  }

}
