Module _20190519

    Sub Main()

        Dim sRead As String = Console.ReadLine()
        Dim iLong As Integer = sRead.Split(" ")(0)
        Dim iOrder As Integer = sRead.Split(" ")(1)
        Dim sStr As String = Console.ReadLine()

        Dim arrChar() As Char = sStr.ToCharArray()

        Dim sNewStr As String = ""

        For i As Integer = 0 To iLong - 1

            If i + 1 = iOrder Then

                Select Case arrChar(i)
                    Case "A"

                        sNewStr = sNewStr & "a"

                    Case "B"

                        sNewStr = sNewStr & "b"

                    Case "C"

                        sNewStr = sNewStr & "c"
                End Select

            Else

                sNewStr = sNewStr & arrChar(i)

            End If

        Next

        Console.WriteLine(sNewStr)

    End Sub

End Module
