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

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		sc.close();
		long d = (long)(b *1000);
		long c = a*d;
		;
		c = c /100;
		System.out.println(new BigDecimal(a).multiply(new BigDecimal(d)).divideToIntegralValue(new BigDecimal("1000")));
	}
}
/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