digraph MT1a {
  node [fontsize="30"];
  edge [labeldistance="1",fontsize="30"];
  "+" [shape="circle"];
  "*" [shape="circle"];
  "-" [shape="circle"];
  "2" [shape="box"];
  "3" [shape="box"];
  "k" [shape="triangle"];
  "m" [shape="triangle"];
  "*" -> "+";
  "*" -> "-";
  "+" -> "k";
  "+" -> "2";
  "-" -> "3";
  "-" -> "m";
}