toplevel "A";
"A" and "B" "C";
"B" lambda=1;
"C" lambda=1;
"F1" fdep "O" "B";
"F2" fdep "O" "C";
"O" or "S" "T";
"S" or "T" "D";
"T" or "E";
"D" lambda=2;
"E" lambda=4;