foo.cc: In function 'int main()':
foo.cc:37:11: warning: unused variable 'j' [-Wunused-variable]
     int i,j,k,n,m;
           ^
foo.cc:37:13: warning: unused variable 'k' [-Wunused-variable]
     int i,j,k,n,m;
             ^
foo.cc:37:15: warning: unused variable 'n' [-Wunused-variable]
     int i,j,k,n,m;
               ^
foo.cc:37:17: warning: unused variable 'm' [-Wunused-variable]
     int i,j,k,n,m;
                 ^

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