digraph CFG {
  node [fontname="Helvetica"];
  n1 [label="START", shape=ellipse, style=filled, color=gray];
  n1 -> n7;
  n7 [label="1", shape=box];
  n7 -> n8;
  n8 [label="2", shape=box];
  n8 -> n9;
  n9 [label="3", shape=box];
  n9 -> n10;
  n10 [label="CALL a", shape=box, style=filled, color=orange];
  n10 -> n3;
  n10 -> n12;
  n3 [label="START a(x, y, z)", shape=ellipse, style=filled, color=green];
  n3 -> n6;
  n6 [label="x", shape=box];
  n6 -> n4;
  n4 [label="END a(x, y, z)", shape=ellipse, style=filled, color=green];
  n4 -> n12;
  n12 [label="RET a", shape=box, style=filled, color=orange];
  n12 -> n2;
  n2 [label="END", shape=ellipse, style=filled, color=gray];
}