Option Strict On
Module Module1

    Sub Main()
        Dim b As String = Console.ReadLine()
        If b = "A" Then
            b = "T"
        ElseIf b = "T" Then
            b = "A"
        ElseIf b = "G" Then
            b = "C"
        Else
            b = "G"

        End If
        Console.WriteLine(b)
        Console.ReadLine()
    End Sub

End Module