1 + 1 * 2 <=> 3
1 * 2 + 3 <=> 5
5 <=> 1 * 2 + 3
(1 + 2) * 3 <=> 9
//-
-1 + 2 <=> 1
-(1 + 2) <=> -3
1 + -1 <=> 0
2 * -1 <=> -2