1: look for at, not found, look for bt, not found, look for ct ...
2: look for [abcdef], found, look for t, not found, look for ght
3: open grouping, look for [abcdef], not found, look for gh, close grouping, found, look for t
4: open grouping, look for a, not found, look for b, not found, look for c, ... look for gh, close grouping, found, look for t.