example:"2*3-4*5"

gives 5 way:

(2*(3-(4*5))) = -34
((2*3)-(4

*5)) = -14*

((2(3-4))

((2

*5) = -10*

(2((3-4)

(2

*5)) = -10*

(((23)-4)*5) = 10

(((2

But you need consider:

2*3-(4*5)=-14

Which has same answer like (2*3)-(4*5)=-14

But not the same. In the first one, we get 4*5 firstly. In the other hand, we get 2*3 firstly.

Why * is missing?