object Main {
  def main(args: Array[String]): Unit = {
    import scala.io.StdIn.readLine
    val Array(datA_, datB_) = readLine.split(" ")
    val datA = datA_.toLong
    val datB = (datB_.toDouble * 100).toLong

    val ans: Long = (datA * datB) / 100
    println(ans)
  }
}
