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

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long a = sc.nextLong();
        double b = sc.nextDouble();
        BigDecimal bd1 = BigDecimal.valueOf(a);
        BigDecimal bd2 = BigDecimal.valueOf(b);
        BigDecimal bd3 = bd1.multiply(bd2);
        BigDecimal sol = bd3.setScale(0, RoundingMode.DOWN);

        System.out.println(sol);
    }
}
/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