foo.cc: In function 'int main()':
foo.cc:27:11: error: 't' was not declared in this scope
     cout<<t;
           ^
foo.cc:18:9: warning: unused variable 'j' [-Wunused-variable]
  ll n,i,j;
         ^

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