import java.io.InputStream;
import java.io.PrintStream;
import java.math.BigDecimal;
import java.util.Scanner;

public class Main {
  public static void main(String[] args) throws Exception {
    solve(System.in, System.out);
  }

  static void solve(InputStream is, PrintStream os) {
    // Your code here!
    Scanner scan = new Scanner(is);
    long A = scan.nextLong();
    Double B = scan.nextDouble();
    BigDecimal BB = new BigDecimal(B.toString());
    BigDecimal BD = BB.multiply(new BigDecimal(A));

    os.println(BD.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