/in/foo.cc: In function 'void dfs1(int, int)':
/in/foo.cc:15:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < g[x].size(); ++i)
                  ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'void dfs2(int, int)':
/in/foo.cc:36:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < g[x].size(); ++i)
                  ~~^~~~~~~~~~~~~