digraph D {
start [shape=box]
end [shape=box]
A [shape=box]
b [shape=box]
c [shape=box]
d [shape=box]
start -> {A, b}
end -> {A, b}
A -> {c, b, end}
A -> {start}
b -> {d, end}
b -> {start, A}
c -> {A}
d -> {b}
}