Drive Direct URL Generator

e = "Error: Invalid URL!"
f = "URL Generator"
Do
a = inputbox("Input sharing URL below", f, a)
If IsEmpty(a) Then
Wscript.Quit
End If
If Len(a) - Len(Replace(a, "/", "")) < 5 Then
MsgBox e, 16, f
Else
b = Split(a, "/")
For c = 0 To 6 Step 1
If b(c) = "d" Then
d = "https://drive.google.com/uc?export=download&id=" & b(c+1)
inputbox "Direct URL has been generated", f, d
Wscript.Quit
End If
Next
MsgBox e, 16, f
End If
Loop