ช่วยดูโค้ด VB ให้หน่อยค่ะ โชว์ค่าmin max แล้วก็ secondmin max

Module Module1

    Sub Main()
        'Dim y As String
        Dim x As Integer
        Dim i As Integer
        Dim score As Integer
        Dim NumF, NumD, NumDD, NumA As Integer
        Dim max, min, max2, min2, sum As Integer
        max = 0
        min = 100
        Dim avg As Double

        While x <> 6
            Console.WriteLine(" ")
            Console.WriteLine("Menu")
            Console.WriteLine("*****************************")
            Console.WriteLine("1. Input and show grade")
            Console.WriteLine("2. Max and SecondaryMax score")
            Console.WriteLine("3. Min and SecondaryMin score")
            Console.WriteLine("4. Average score")
            Console.WriteLine("5. Show Frequency of each grade")
            'Console.WriteLine("6. Enter Exit")
            Console.WriteLine("Enter choice : ")

            x = Console.ReadLine
            If x = 1 Then
                Console.WriteLine("Input and show grade")
                For i = 1 To 10 Step 1
                    'รับค่า

                    Console.Write("Enter int score no :" & i & " ")
                    score = Console.ReadLine

                    While score < 0 Or score > 100
                        Console.WriteLine("Invalid")
                        Console.Write("Enter int score no :" & i & " ")
                        score = Console.ReadLine
                    End While


                    sum = sum + score
                    Select Case score
                        Case 0 To 50
                            Console.WriteLine("F")
                            NumF += 1 'นับสะสมทีละ1
                            'NumF = NumF + 1'
                        Case 51 To 60
                            Console.WriteLine("D")
                            NumD += 1
                        Case 61 To 70
                            Console.WriteLine("D+")
                            NumDD += 1
                        Case 71 To 100
                            Console.WriteLine("A")
                            NumA += 1
                    End Select
                Next
            End If
            If x = 2 Then
                Console.WriteLine("Max and SecondaryMax score")
                Console.WriteLine("- - - - - - - - - - - - - -")
                If score > max Then
                    max2 = max
                    max = score
                ElseIf score > max2 Then
                    max2 = score
                End If
            End If

            If x = 3 Then
                Console.WriteLine("Min and SecondaryMin score")
                Console.WriteLine("- - - - - - - - - - - - - -")
                If score < min Then
                    min2 = min
                    min = score
                ElseIf score < min2 Then
                    min2 = score
                End If
            End If
            If x = 4 Then
                Console.WriteLine("Average score")
                Console.WriteLine("- - - - - - - - - - - - - - -")
                avg = sum / 10
                Console.WriteLine("Average score = " & avg)
            ElseIf x = 5 Then
                Console.WriteLine("Show Frequency of each grade")
                Console.WriteLine("- - - - - - - - - - - - - - -")
                Console.WriteLine("Number of grade A = " & NumA)
                Console.WriteLine("Number of grade D+ = " & NumDD)
                Console.WriteLine("Number of grade D = " & NumD)
                Console.WriteLine("Number of grade F = " & NumF)
            End If

        End While

    End Sub

End Module