EnableExplicit
Define.i i

If OpenConsole("")
  PrintN("Stern-Brocot_sequence")
Else
  End 1
EndIf

Procedure.i f(n.i)
  If n<2
    ProcedureReturn n
  ElseIf n&1
    ProcedureReturn f(n/2)+f(n/2+1)
  Else
    ProcedureReturn f(n/2)
  EndIf
EndProcedure

Procedure.i gcd(a.i,b.i)
  If b : ProcedureReturn gcd(b,a%b) : EndIf
  ProcedureReturn a
EndProcedure

Procedure.i ind(m.i)
  Define.i i=1
  While f(i)<>m : i+1 : Wend
  ProcedureReturn i
EndProcedure

Print("First 15 elements: ")
For i=1 To 15
  Print(Str(f(i))+Space(3))
Next
PrintN(~"\n")

For i=1 To 10
  PrintN(RSet(Str(i),3)+" is at pos. #"+Str(ind(i)))
Next
PrintN("100 is at pos. #"+Str(ind(100)))
PrintN("")

i=1
While i<1000 And gcd(f(i),f(i+1))=1 : i+1 : Wend
If i=1000
  PrintN("All GCDs are 1.")
Else
  PrintN("GCD of "+Str(i)+" and "+Str(i+1)+" is not 1")
EndIf

Input()