How to Put Negative Sign in Front in SAP ABAP Report ?

How to Put Negative Sign in Front in SAP  ABAP Report ?

Use Function Module CLOI_PUT_SIGN_IN_FRONT

REPORT Ztest.

PARAMETERS v_amount(10) TYPE c OBLIGATORY DEFAULT '1000.50-'.

WRITE:/ 'Before using FM:', v_amount.

CALL FUNCTION 'CLOI_PUT_SIGN_IN_FRONT'
  CHANGING
    value = v_amount.

WRITE:/ 'After using FM:', v_amount.