A grade: { }
B grade: { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21, 26, 28, 29, 34, 38, 39, 40, 42, 43, 44, 46, 47, 49, 51, 52, 54, 56, 57, 59 }
C grade: { }
F grade: { 15, 22, 23, 24, 25, 27, 30, 31, 32, 33, 35, 36, 37, 41, 45, 48, 50, 53, 55, 58, 60, 61, 62, 63, 64 }