import java.io.*;
import java.util.*;
public class Main
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		Long a = Long.parseLong(st.nextToken());
		String b = (st.nextToken());
		long b1 = Long.parseLong(b.substring(0,b.indexOf('.'))+b.substring(b.indexOf('.')+1));
		//System.out.println(b1); 
		System.out.println((a*b1)/100);
	}
}
/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