import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    long a = Long.parseLong(sc.next());
    char[] b = sc.next().toCharArray();
    int c = 100*(b[0]-'0')+10*(b[2]-'0')+b[3]-'0';
    System.out.println(a*c/100);
  }
} import java.util.*; util.* java class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    long a = Long.parseLong(sc.next());
    char[] b = sc.next().toCharArray();
    int c = 100*(b[0]-'0')+10*(b[2]-'0')+b[3]-'0';
    System.out.println(a*c/100);
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    long a = Long.parseLong(sc.next());
    char[] b = sc.next().toCharArray();
    int c = 100*(b[0]-'0')+10*(b[2]-'0')+b[3]-'0';
    System.out.println(a*c/100);
  } main {
    Scanner sc = new Scanner(System.in);
    long a = Long.parseLong(sc.next());
    char[] b = sc.next().toCharArray();
    int c = 100*(b[0]-'0')+10*(b[2]-'0')+b[3]-'0';
    System.out.println(a*c/100);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = Long.parseLong(sc.next()); a Long.parseLong(sc.next()) Long.parseLong Long sc.next() sc.next sc char[] b = sc.next().toCharArray(); b sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc int c = 100*(b[0]-'0')+10*(b[2]-'0')+b[3]-'0'; c 100*(b[0]-'0')+10*(b[2]-'0')+b[3]-'0' 100*(b[0]-'0')+10*(b[2]-'0')+b[3] 100*(b[0]-'0')+10*(b[2]-'0')+b[3] 100*(b[0]-'0') 100 (b[0]-'0') b[0] b 0 '0' 10*(b[2]-'0') 10 (b[2]-'0') b[2] b 2 '0' b[3] b 3 '0' System.out.println(a*c/100) System.out.println System.out System System.out a*c/100 a*c a c 100 String[] args args
import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    long a = Long.parseLong(sc.next());
    char[] b = sc.next().toCharArray();
    int c = 100*(b[0]-'0')+10*(b[2]-'0')+b[3]-'0';
    System.out.println(a*c/100);
  }
}