import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String vSt = sc.next();
        String []arr=vSt.split("\\.");
        int v = Integer.parseInt(arr[1]);
        int t = sc.nextInt();
        int d = v*t/10000;
        System.out.println(d);
    }
}