N is Fibinacci if one of 5 * n * n + 4 or 5 * n * n - 4 or both are perferct square
x = 5 * n * n NEW_LINE if ( isPerfectSquare ( x + 4 ) or isPerfectSquare ( x - 4 ) ) : NEW_LINE INDENT return 0 NEW_LINE DEDENT else : NEW_LINE INDENT return n NEW_LINE DEDENT