import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = sc.nextLong();
		String b = sc.next();
		String d = "";
		
		for(int i = 0; i< b.length(); i++) {
			if(b.charAt(i) == '.') {
				continue;
			}
			d+=b.charAt(i);
		}
		int c= new Integer(d).intValue();
		System.out.println(a*c/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