import java.math.BigDecimal;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigDecimal a = new BigDecimal(scanner.nextLong());
        String tmp = scanner.next().replace(".","");
        BigDecimal b = new BigDecimal(Long.valueOf(tmp));

        System.out.println(a.multiply(b).divide(new BigDecimal(100)).longValue());

    }
}
/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