Maxima

A grade

{ 2, 4, 5, 6, 7, 9, 11, 13, 14, 16, 18, 19, 20 }

B grade

{ 1, 3, 8 }

C grade

{ }

F normal fail

{ 21 }

F(-1) timedout fail

{ }

F(-2) exception fail

{ 10, 12, 15, 17 }