foo.cc: In function 'int main()':
foo.cc:6:17: warning: unused variable 'o' [-Wunused-variable]
  int n,a[10010],o=0;
                 ^
foo.cc:13:11: warning: unused variable 't' [-Wunused-variable]
  int ls=1,t=0;
           ^

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