import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
        Scanner scn = new Scanner(System.in);
        long a = scn.nextLong();
        double b = scn.nextDouble();
        double b2 = Math.round(b*100);

        long B = (long)b2;

        long ans = a*B;

        long ans2 = ans/100;

        System.out.println(ans2);

        scn.close();


    }


}
/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