A->A*B {1}
A->E {A.val=E.val}
B->C+D {2}
C->C-D {C.val=D.val.+C.val}
D->D-E {D.val=D.val+E..val}
E->E/F {3}
F->G {F.val=G.val}
A,B,C,D,E,F,G->id {A.val->id,B.val->id,C.val->id,D.val->id,E.val->id,F.val->id,G.val->id}
Fill 1 ,2 and 3 so that for:6*4-3-5/4+12 it outputs 32.