timestamps (d/f) in the order the DFS assigned them
  shirt         1/8
  tie           2/5
  jacket        3/4
  belt          6/7
  watch         9/10
  undershorts  11/16
  pants        12/15
  shoes        13/14
  socks        17/18
back edge found: no
topological order: socks undershorts pants shoes watch shirt belt tie jacket 
check: every edge points forward
  all 9 edges satisfied
