-expr = int | int add int # expr1 and #expr2
\ No newline at end of file
+single = "(" expr ")" | int
+args = single , args | single
+callees = "(" args ")" | "(" ")"
+facAux = callees facAux | callees
+single facAux | single
+fac = single facAux | single
+term = fac | fac (MUL | DIV) fac
+expr = term (ADD | SUB) term