foo.cc: In function 'void BFS(int, int, int, int)':
foo.cc:12:6: warning: unused variable 'step' [-Wunused-variable]
   12 |  int step = 1;
      |      ^~~~
foo.cc:15:7: warning: variable 'x' set but not used [-Wunused-but-set-variable]
   15 |  bool x = true;
      |       ^
foo.cc: In function 'int main()':
foo.cc:62:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   62 |  scanf("%d%d\n",&w,&h);
      |  ~~~~~^~~~~~~~~~~~~~~~
foo.cc:90:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   90 |   scanf("%d%d%d%d",&x,&y,&xx,&yy);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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