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;
      |                 ^
foo.cc:7:17: warning: ‘i’ is used uninitialized [-Wuninitialized]
    7 |         for(int i=i;i<=n;i++)
      |                 ^
foo.cc:7:17: note: ‘i’ was declared here
    7 |         for(int i=i;i<=n;i++)
      |                 ^