program Rec9;
{ recursive (n+(n-1)+(n-2)+...+3+2+1) function example      }
{ exemplo de funcao (n+(n-1)+(n-2)+...+3+2+1) recursiva     }
{ Turbo Pascal 7 source        }
{ Free Pascal Source           }
{ Delphi Source                }
{ Joao Paulo Schwarz Schuler   }
{ http://www.schulers.com/jpss }


function RSerie(X:longint):longint;
begin

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

end;

begin
Writeln(RSerie(-5));   {-15 }
Writeln(RSerie(5));    { 15 }

Writeln(RSerie(0));    { 0  }
Writeln(RSerie(1));    { 1  }
Writeln(RSerie(50));   { 1275 }

end.