[1,2,3,2,4,3,5,6,3,4,7,5,4,6,8,9,4,5,7,6,10,5,8, 11,7,6,5,9,12,13,8,6,7,9,10,11,14,6,7,8,10,12,9, 13,15,7,8,11,16,17,10,9,7,12,8,13,11,14,18,15,9, 10,8,19,12,14,16,11,13,9,8,10,17,20,15]