i aaa aaa --------------------------- a bbb aaa bbb --------------------------- a ccc aaa bbb ccc --------------------------- a ddd aaa bbb ccc ddd --------------------------- a eee aaa bbb ccc ddd eee --------------------------- u aaa bbb ccc ddd --------------------------- u aaa bbb ccc --------------------------- a fff aaa bbb ccc fff --------------------------- a ggg aaa bbb ccc fff ggg --------------------------- u aaa bbb ccc fff --------------------------- --------------------------- u aaa bbb ccc g- aaa bbb ccc ddd --------------------------- --------------------------- u aaa bbb g- aaa bbb ccc ddd eee --------------------------- --------------------------- u aaa g- aaa bbb ccc ddd --------------------------- --------------------------- g- aaa bbb ccc --------------------------- --------------------------- g- aaa bbb --------------------------- --------------------------- g- aaa --------------------------- ---------------------------