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

    public static void main(String []args)
    {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        double b = sc.nextDouble();
        BigDecimal c = new BigDecimal(a);
        BigDecimal d = BigDecimal.valueOf(b);
        System.out.println(c.multiply(d).toBigInteger());
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz