program Rec5;
{ recursive double function example    }
{ exemplo de funcao dobra recursiva }
{ Turbo Pascal 7 source        }
{ Free Pascal Source           }
{ Delphi Source                }
{ Joao Paulo Schwarz Schuler   }
{ http://www.schulers.com/jpss }


function RDobra(X:word):word;
begin

if X=0
   then RDobra:=0
   else RDobra:=2+RDobra(X-1);

end;

begin
Writeln(RDobra(0));     { 0  }
Writeln(RDobra(1));     { 2  }
Writeln(RDobra(10));    { 20  }
end.