foo.cc: In function 'void init()':
foo.cc:18:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d",&L,&s,&t,&n);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:20:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&stone[i]);
         ~~~~~^~~~~~~~~~~~~~~~

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