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