Module Program
    Public Class Complex
        Public Property RPart As Double ' Real part
        Public Property IPart As Double  ' Imaginary part

        ' Constructor to create a complex number
        Public Sub New(r As Double, i As Double)
            RPart = r
            IPart = i
        End Sub

        ' Method to convert complex number to string representation
        Public Overrides Function ToString() As String
            If IPart < 0 Then
                Return RPart.ToString() & IPart.ToString() & "i"
            Else
                Return RPart.ToString() & "+" & IPart.ToString() & "i"
            End If
        End Function

        ' Static method to parse string representation into a complex number
        Public Shared Function StrCpx(s As String) As Complex
            Dim i As Integer = s.IndexOfAny(New Char() {"+"c, "-"c}, 1)

            ' Check if we found a valid index
            If i < 0 Then
                ' If no '+' or '-' was found after the first character, return real part only
                Return New Complex(Double.Parse(s), 0)
            End If

            ' Get the real part and imaginary part correctly
            Dim realPart As Double = Double.Parse(s.Substring(0, i))
            Dim imagPartStr As String = s.Substring(i)

            ' Handle cases for the imaginary part, ensuring we strip the "i"
            Dim imagPart As Double = Double.Parse(imagPartStr.Replace("i", "").Trim())

            ' Returning the constructed complex number
            Return New Complex(realPart, imagPart)
        End Function

        ' Method to add two complex numbers
        Public Shared Function CpxAdd(x1 As Complex, x2 As Complex) As Complex
            Return New Complex(x1.RPart + x2.RPart, x1.IPart + x2.IPart)
        End Function

        ' Method to subtract second complex number from the first
        Public Shared Function CpxSub(x1 As Complex, x2 As Complex) As Complex
            Return New Complex(x1.RPart - x2.RPart, x1.IPart - x2.IPart)
        End Function

        ' Method to multiply two complex numbers
        Public Shared Function CpxMul(x1 As Complex, x2 As Complex) As Complex
            Dim r As Double = x1.RPart * x2.RPart - x1.IPart * x2.IPart
            Dim i As Double = x1.RPart * x2.IPart + x1.IPart * x2.RPart
            Return New Complex(r, i)
        End Function

        ' Method to divide first complex number by the second
        Public Shared Function CpxDiv(x1 As Complex, x2 As Complex) As Complex
            Dim denom As Double = x2.RPart ^ 2 + x2.IPart ^ 2
            Dim r As Double = (x1.RPart * x2.RPart + x1.IPart * x2.IPart) / denom
            Dim i As Double = (x1.IPart * x2.RPart - x1.RPart * x2.IPart) / denom
            Return New Complex(r, i)
        End Function
    End Class

    Sub Main()
        ' Create some complex numbers
        Dim c1 As New Complex(3, 4) ' 3 + 4i
        Dim c2 As New Complex(1, -2) ' 1 - 2i

        ' Display the complex numbers
        Console.WriteLine("c1: " & c1.ToString())
        Console.WriteLine("c2: " & c2.ToString())

        ' Addition
        Dim sum As Complex = Complex.CpxAdd(c1, c2)
        Console.WriteLine("c1 + c2: " & sum.ToString())

        ' Subtraction
        Dim difference As Complex = Complex.CpxSub(c1, c2)
        Console.WriteLine("c1 - c2: " & difference.ToString())

        ' Multiplication
        Dim product As Complex = Complex.CpxMul(c1, c2)
        Console.WriteLine("c1 * c2: " & product.ToString())

        ' Division
        Dim quotient As Complex = Complex.CpxDiv(c1, c2)
        Console.WriteLine("c1 / c2: " & quotient.ToString())

        ' Convert string to complex
        Dim c3 As Complex = Complex.StrCpx("5-6i")
        Console.WriteLine("c3 (from string): " & c3.ToString())

        ' Wait for a key press before closing
        Console.WriteLine("Press any key to continue...")
        Console.ReadKey() ' Wait for a key press
    End Sub
End Module