Choose the correct frequency for every line as well as the total $O$ of the following code:

int sum $=0$;

for $($into i $=0$; i $$ n $*$ n; i$++)$

for $($int $j=n-1$;$jn-1-i$;$j--\{$

sum $=$ i$+$ j;

system.out.println$($sum$)$ ;$\}$