foo.cc: In function 'int main()':
foo.cc:7:9: warning: unused variable 'i' [-Wunused-variable]
     int i,j;
         ^
foo.cc:7:11: warning: unused variable 'j' [-Wunused-variable]
     int i,j;
           ^

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