/in/foo.cc: In function 'void DFS(int)':
/in/foo.cc:10:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int k=0;k<g[i].size();k++){
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'void DFS2(int)':
/in/foo.cc:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int k=0;k<g[i].size();k++){
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'void DFS4(int)':
/in/foo.cc:28:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int k=0;k<g[i].size();k++){
               ~^~~~~~~~~~~~