import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();

        BigDecimal ans = null;
        BigDecimal bda = new BigDecimal(a);
        bda.setScale(0);
        BigDecimal bdb = new BigDecimal(b);
        bdb.setScale(2, RoundingMode.DOWN);
        ans = bda.multiply(bdb);
        System.out.println(ans.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