foo.cc: In function 'int bfs_1(int, int, int*, int*)':
foo.cc:58:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<cw[now].size();i++)
                      ~^~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:98:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<cw.size();i++)
                      ~^~~~~~~~~~
foo.cc:105:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<cw.size()-1;i++)
                      ~^~~~~~~~~~~~
foo.cc:110:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d%d%d",&x,&y,&v);
             ~~~~~^~~~~~~~~~~~~~~~~~~

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