Module Program
Sub Main(args As String())
        Dim iInput As String() = Split(Console.ReadLine(), " ")
        Dim iA As Double = Integer.Parse(iInput(0))
        Dim iB As Double = Integer.Parse(iInput(1))
        Dim iH As Double = Integer.Parse(iInput(2))
        Dim iM As Double = Integer.Parse(iInput(3))

        Dim rad As Double = Math.PI * 2 * ((iH / 12) + (iM / 720) - (iM / 60))

        Dim sq As Double = (iA ^ 2 + iB ^ 2) - (2 * iA * iB) * Math.Cos(rad)

        Console.WriteLine(Math.Sqrt(sq))


    End Sub
End Module