One less guard in euclid for same effect

chapter-1/euclid.lisp

@@ -13,7 +13,7 @@
 
 (defun euclid (m n)
   "Calculates the greatest common divisor between m and n"
-  (when (or (= m 0) (= n 0) (> 0 m n))
+  (when (or (>= 0 m) (>= 0 n))
     (return-from euclid nil))
   (if (< m n)
       (euclid n m)