foo.cc: In function 'int bfs_1(int, int, int*, int*)':
foo.cc:55:18: 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:91:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i=0; i<cw.size(); i++) {
                 ~^~~~~~~~~~
foo.cc:100:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&v);
    ~~~~~^~~~~~~~~
foo.cc:108:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&cost);
     ~~~~~^~~~~~~~~~~~

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