A grade: { 4, 5, 8, 9, 10, 13, 14, 15, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 55, 56, 57, 60, 61, 62, 65, 66, 67, 71, 72, 76, 77 }
B grade: { 1, 2, 3, 6, 7, 11, 12, 53, 54, 58, 59, 63, 64, 68, 69, 70, 73, 74, 75 }
C grade: { }