import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            long A = sc.nextLong();
            String B = sc.next();
            String[] split = B.split("[.]");
            long B1 = Long.parseLong(split[0]);
            long B2 = Long.parseLong(split[1]);
            long B3 = B1 * 100 + B2;
            System.out.println((A * B3) / 100);
        }
    }
}

/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