/in/foo.cc: In function 'int main()':
/in/foo.cc:41:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<bl[root].size();i++)
              ~^~~~~~~~~~~~~~~~
/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:63:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<tree[x].size();i++)
              ~^~~~~~~~~~~~~~~
/in/foo.cc: In function 'void ss(int)':
/in/foo.cc:80:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<bl[x].size();i++)
              ~^~~~~~~~~~~~~