import java.util.*;
import java.math.*;
class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        long a = Long.parseLong(sc.next());
        double b = Double.parseDouble(sc.next());
        b*=500;
        long c = (long)b;
        System.out.println(a*c/500);
    }
}
/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