6-12 $f(n)$ is a function defined on the set of positive integers, taking non-negative integer values, and for all $m, n$ we have:
$$
\begin{array}{l}
f(m+n)-f(m)-f(n)=0 \text { or } 1 ; \\
f(2)=0, f(3)>0, f(9999)=3333 .
\end{array}
$$

Try to find: $f(1982)$.