path from 4 to 4: 4
path from 9 to 4: 9 6 14 13 4
path from 4 to 9: 4 13 14 6 9
path from 7 to 15: 7 2 5 13 15
path from 5 to 6: 5 13 14 6
path from 3 to 13: 3 11 14 13

path from 1 to 2: 1 2