
import java.math.BigInteger;
import java.util.*;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		long a = Long.parseLong(sc.next());
		long b = Long.parseLong(sc.next().replace(".", ""));

		BigInteger bigA = BigInteger.valueOf(a);
		BigInteger bigC = bigA.multiply(BigInteger.valueOf(b));
		BigInteger bigD = bigC.divide(BigInteger.valueOf(100));
		
		System.out.println(bigD.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