object Main {
  def main(args:Array[String]) {
    val abx = readLine().split(' ').map(_.toInt)
    val a = abx(0)
    val b = abx(1)
    val x = abx(2)
    val aab = a * a * b
    val h = x.toDouble / a.toDouble / a.toDouble
    val degree = Math.toDegrees(Math.atan(
      if(b < h * 2) (b - h) * 2d / a
      else b * b / a / h / 2d))
    println(degree)
  }
}
