@startuml
skinparam defaultTextAlignment center

(3) as q1
(5) as q2
(3) as q3

card "x" as mul
card "-" as neg1
card "-" as neg2
card "+" as sum1
card "+" as sum2

q1 -d-> mul
mul -r-> sum1
q2 -d-> neg1
neg1 -d-> sum1
sum1 -r-> neg2: b
neg2 -d-> sum2
q3 -l-> sum2
sum2 -u-> mul: a
@enduml
