import java.io.{BufferedReader, InputStreamReader}

object Main {
  def main(args: Array[String]): Unit = {
    val Array(a, b, x) = new BufferedReader(new InputStreamReader(System.in)).readLine().split("\\s+").map(_.toDouble)

    val h = x / a / a

    val degree = Math.toDegrees(Math.atan(
      if (b < h * 2) {
        (b - h) * 2.0 / a
      } else {
        b * b / a / h / 2.0
      }
    ))

    System.out.println(f"$degree%2.10f")
  }
}
