import java.util.*;

class Main {

	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
      long A =sc.nextLong(),ans=0;
      String B = sc.next();
      ans += 100*A*Character.getNumericValue(B.charAt(0));
      ans += 10*A*Character.getNumericValue(B.charAt(2));
      ans += A*Character.getNumericValue(B.charAt(3));
      System.out.println(ans/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