' version 19-01-2019
' compile with: fbc -s console

Const As Integer max = 1000000
Randomize Timer

Dim As UInteger i, car_door, chosen_door, montys_door, stay, switch

For i = 1 To max
    car_door = Fix(Rnd * 3) + 1
    chosen_door = Fix(Rnd * 3) + 1
    If car_door <> chosen_door Then
        montys_door = 6 - car_door - chosen_door
    Else
        Do
          montys_door = Fix(Rnd * 3) + 1
        Loop Until montys_door <> car_door
    End If
    'Print car_door,chosen_door,montys_door
    ' stay
    If car_door = chosen_door Then stay += 1
    ' switch
    If car_door = 6 - montys_door - chosen_door Then switch +=1
Next

Print Using "If you stick to your choice, you have a ##.## percent" _
                                         + " chance to win"; stay / max * 100
Print Using "If you switched, you have a ##.## percent chance to win"; _
                                                           switch / max * 100

' empty keyboard buffer
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End