
Illustration of the cases in Theorem 1. The graph in the figure represents
, where k = 3 and
. The segments are marked by dashed lines with their starts marked with a dot and their ends marked with a diamond. The unitig
w = {ACT, CTT, TTG} is unsafe because for each of the segment, one of the cases in Theorem 1 is true. For segment colored in green, case 1 holds;
for red, case 2; for blue, case 3; and for orange, case 4.











