Imports System
Public Module Module1
Function contain_only_three_same_repeating_chars(s As String) As Boolean
Dim len As Integer = s.Length
if (len Mod 3 <> 0) Then return false
For i As Integer = 0 To len - 4
If (s(i) <> s(i + 3)) Then return false
Next
return true
End Function
Public Sub Main()
Dim s As String = "vbnvbnvbnvbnvbnvbnvbn"
If (contain_only_three_same_repeating_chars(s)) Then
Console.WriteLine("Yes")
else
Console.WriteLine("No")
End If
End Sub
End Module
' Run
'
' Yes
'