ABAP : Fibonuci

DATA result TYPE i.

PERFORM get_fibo USING 5 CHANGING result.
WRITE result.

FORM get_fibo USING p_num changing result.
  DATA : lv_1 TYPE i,
         lv_2 TYPE i.

  IF p_num = 0.
    result = 0.
    exit.
  ELSEIF p_num = 1.
    result = 1.
    exit.
  ENDIF.

  lv_1 = p_num - 1.
  lv_2 = p_num - 2.

  PERFORM get_fibo USING lv_1 CHANGING lv_1.
  PERFORM get_fibo USING lv_2 CHANGING lv_2.
  result = lv_1 + lv_2.

ENDFORM.