Imports System

Public Module Module1

    Public Sub Main()

        dim mark1 as decimal

        console.writeline("enter mark")

        mark1=console.readline()

        do while mark1 > 100 or mark1 < 0

            console.writeline("please enter mark between 0 - 100")

            console.writeline("enter mark")

            mark1=console.readline()

        loop

        select case mark1

        case is >=75

            console.writeline("grade A")

        case is >=50

            console.writeline("grade B-C")

        case is >=25

            console.writeline("grade D-E")

        case is <25

            console.writeline("grade U")

    end select

    End Sub

End Module