Imports System

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Public Module Module1

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    Public Sub Main()

        Dim n1, length as integer

        length = 0

        Do

            Console.WriteLine("Input a number")

            n1 = console.ReadLine()

            if n1 > length

                length = n1

            end if

        loop until n1 = "-1"

​

        Console.WriteLine(length)

    End Sub

End Module

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