foo.cc: In function 'int main()':
foo.cc:63:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf( "%d%d", &n, &k );
     ~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:69:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             char ch; scanf( "%c", &ch );
                      ~~~~~^~~~~~~~~~~~~
foo.cc:78:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int x, y; scanf( "%d%d", &x, &y );
                   ~~~~~^~~~~~~~~~~~~~~~~~

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