foo.cc: In function ‘int main()’:
foo.cc:5:15: warning: unused variable ‘i’ [-Wunused-variable]
    5 |         int n,i,j;
      |               ^
foo.cc:5:17: warning: unused variable ‘j’ [-Wunused-variable]
    5 |         int n,i,j;
      |                 ^