ABAP - Function Module To Change Sign Of Values - 'CLOI_PUT_SIGN_IN_FRONT'

data: a1 type i value 56,
a2 type i value 60,
res type i,
res1(10).res = a1 - a2.
res1 = res.

CALL FUNCTION 'CLOI_PUT_SIGN_IN_FRONT' CHANGING VALUE = res1
write res1.