foo.cc: In function 'int main()':
foo.cc:13:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("rabbit.in","r",stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
foo.cc:14:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("rabbit.out","w",stdout);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:32:23: warning: 'VALUE' may be used uninitialized in this function [-Wmaybe-uninitialized]
      if(vst[x2][y2]==0&&VALUE>a[x2][y2])
         ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
foo.cc:34:45: warning: 'xxx' may be used uninitialized in this function [-Wmaybe-uninitialized]
       if(xxx+pow(abs(x1[xxx]-x2)+abs(yy1[xxx]-y2),2)>f[i][j])
                                      ~~~~~~~^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。