求 N1,N2 的最大公因數

'求 N1,N2 的最大公因數
Public Class Form1
    Dim i
    Dim str1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim n1 = 24
        Dim n2 = 60

        'Dim n1 = Val(InputBox("請輸入第一個數："))
        'Dim n2 = Val(InputBox("請輸入第二個數："))

        For i = 1 To n1
            If n1 Mod i = 0 And n2 Mod i = 0 Then
                str1 = i
            End If
        Next
        MsgBox(str1)
    End Sub
End Class