G = _VT,VN,P,S_, dove:
VT = { 0,1,2,3,4,5,6,7,8,9,+,- }
VN = {, , , }
P = {
::= [+|-] ::= 0 | {} ::= 0 | ::= 1|2|3|4|5|6|7|8|9
}