import java.util.*;

public class Main {
	public static void main(String[] args) {

		Scanner keyboard = new Scanner(System.in);

		long A = keyboard.nextLong();
		String B = keyboard.next();
		
		long NB = 0;
		String nb = "";
		
		for(int b = 0;b<4; b++) {
			if( B.charAt(b)!= '.') {
				nb += B.charAt(b);
			}
		}
		NB = Integer.parseInt(nb);
		
		System.out.println(NB*A/100);
		keyboard.close();
	}
}
/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