/in/foo.cc: In function 'void DFS2(int, int)':
/in/foo.cc:55:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<lay[nowlay].size();i++)
              ~^~~~~~~~~~~~~~~~~~~
/in/foo.cc:68:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<lay[nowlay].size();i++)
              ~^~~~~~~~~~~~~~~~~~~
/in/foo.cc:78:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<lay[nowlay].size();i++) p[lay[nowlay][i]].infect=false;
              ~^~~~~~~~~~~~~~~~~~~