For any positive integer $$k$$, let $$f_1(k)$$ denote the square of the sum of the digits of $$k$$. For $$n \ge 2$$, let $$f_n(k) = f_1(f_{n - 1}(k))$$. Find $$f_{1988}(11)$$.

(第六届AIME1988 第2题)