feat/ improve order

Co-authored-by: MaoShizhong <[email protected]>

Author: nik-rev

13_factorial/README.md

@@ -5,8 +5,8 @@ Write a recursive function that takes a non-negative integer, and returns the pr
 For example:
 
 ```javascript
-factorial('4'); // Output: undefined
 factorial(5); // 5 * 4 * 3 * 2 * 1, Output: 120
-factorial(7.2); // Output: undefined
 factorial(0); // Output: 1
+factorial(7.2); // Output: undefined
+factorial('4'); // Output: undefined
 ```