program Rec3;
{ recursive identity function example    }
{ exemplo de funcao identidade recursiva }
{ Turbo Pascal 7 source        }
{ Free Pascal Source           }
{ Delphi Source                }
{ Joao Paulo Schwarz Schuler   }
{ http://www.schulers.com/jpss }


function RIdentity(X:integer):integer;
begin

if X>=0
   then begin
        if X=0
           then RIdentity:=0
           else RIdentity:=1+RIdentity(X-1);
        end
   else RIdentity:=-1+RIdentity(X+1);

end;



begin
Writeln(RIdentity(-5));
Writeln(RIdentity(0));
Writeln(RIdentity(5));
end.