Let
be a function defined on the set of all positive integers and having its values in the same set. Suppose that
for all positive integers
Find the possible value for
%V0
Let $f(n)$ be a function defined on the set of all positive integers and having its values in the same set. Suppose that $f(f(n) + f(m)) = m + n$ for all positive integers $n,m.$ Find the possible value for $f(1988).$
Školjka