foo.cc: In function 'int main()':
foo.cc:15:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf( "%d %d" , &n , &k );
 ~~~~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:19:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf( "%d" , &s[j] );
 ~~~~~^~~~~~~~~~~~~~~~

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