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

public class Main {

    public static void main(String[] args) {
        exec();
    }

    static void exec() {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        double m = sc.nextDouble();

        BigDecimal b = BigDecimal.valueOf(n);
        BigDecimal c = BigDecimal.valueOf(m);
        System.out.println(b.multiply(c).setScale(0, BigDecimal.ROUND_DOWN));
    }
}
/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