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