/in/foo.cc: In function 'int build_tree(int)':
/in/foo.cc:25:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < t[s].size(); i++) {
                     ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'int dfs(int*)':
/in/foo.cc:46:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int j = 0; j < map[bri].size(); j++)
                             ~~^~~~~~~~~~~~~~~~~