digraph AddVariables {
node1 [label="Start", color="#2e3436"]
node3 [label="a = 1, b = 1", color="#2e3436"]
node4 [label="b += a", color="#2e3436"]
node2 [label="End", color="#2e3436"]

node1 -> node3
node3 -> node4
node4 -> node2
}