Maxima

A grade

{ 6, 8, 10, 12, 16, 17, 18, 19 }

B grade

{ 5, 7, 9, 11, 13, 14, 21 }

C grade

{ 15, 20 }

F normal fail

{ }

F(-1) timedout fail

{ }

F(-2) exception fail

{ 1, 2, 3, 4 }