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

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        long a = sc.nextLong();
        BigDecimal ba = BigDecimal.valueOf(a);
        String b = sc.next();
        BigDecimal bb = new BigDecimal(b);


        System.out.println(ba.multiply(bb).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