Public Class Program
  Shared Sub Main()
    Dim abx As Double() = Array.ConvertAll(Of String, Double)(Console.ReadLine().Split(" "), AddressOf Double.Parse)
    Dim a As Double = abx(0)
    Dim b As Double = abx(1)
    Dim x As Double = abx(2)
    Dim tan As Double = If(x < a * a * b / 2, a * b * b / (2 * x), 2 * (a * a * b - x) / (a * a * a))
    Console.WriteLine(Math.Atan(tan) * 180 / Math.PI)
  End Sub
End Class