import java.util.Scanner;

/*

*/

public class Main {
    public static void main(String[] args){

        Scanner sc = new Scanner(System.in);
        long a = sc.nextLong();
        double b = sc.nextDouble();
        long bb = Math.round(b * 100);
//        System.out.println(b * 100);
//        System.out.println(Math.floor(b * 100));
        long ans = a * bb / 100;

        System.out.println(ans);

    }
}
/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