toplevel "A";
"A" or "B" "C";
"B" or "BE1" "BE2";
"C" or "BE3" "BE4";
"BE1" lambda=0.5 dorm=3;
"BE2" lambda=0.5 dorm=3;
"BE3" lambda=0.5 dorm=3;
"BE4" lambda=0.5 dorm=3;