Как исправить ошибку «Арифметическая операция привела к переполнению»

Всякий раз, когда я хочу узнать оценку в программе, которую я сделал.
Он выделяет утверждение k = k + 1 и говорит:

Arithmetic operation resulted in an overflow

Кто-нибудь может помочь?

Sub SearchStudentData()
    Dim Sname, G As String
    Dim Lname, Lgradetext, position, j, k, position1 As Integer
    Dim gradefile As IO.StreamReader
    Dim Valid As Boolean
    Valid = False
    Console.WriteLine("Enter the name of the student of whom you want the grade!")
    Sname = Console.ReadLine()
    Lname = Len(Sname)
    gradefile = New IO.StreamReader("D:\Grades.txt")
    Do Until gradefile.EndOfStream
        gradetext = gradefile.ReadLine()
        Lgradetext = Len(gradetext)
        j = 0
        k = 0
        Do
            k = k + 1      'It highlights this line of code
            position1 = k
        Loop Until Mid(gradetext, k, 1) = ":"
        Do
            j = j + 1
            position = j
        Loop Until Mid(Lgradetext, j, 1) = ","
        If Sname = Right(gradetext, position1 + 1) And Sname = Left(gradetext, position - 1) Then
            Valid = True
        End If
        If Valid = True Then
            G = Right(Lgradetext, Lgradetext - 1)
            Console.WriteLine(G)
        Else
            Valid = False
            Console.WriteLine("Ypu have failed this PROGRAM")
        End If
    Loop
    gradefile.Close()
End Sub