Add 'usaco/' from commit '00738523fb2634fee57a1c476b324247633a6898'

git-subtree-dir: usaco
git-subtree-mainline: f72f8b96e6ca9b552ad448d0b9298fcbb0302825
git-subtree-split: 00738523fb2634fee57a1c476b324247633a6898