Update Readme.md

Author: wisdompeak

Readme.md

@@ -329,7 +329,7 @@
 [1306.Jump-Game-III](https://github.com/wisdompeak/LeetCode/tree/master/DFS/1306.Jump-Game-III) (M) 
 [1718.Construct-the-Lexicographically-Largest-Valid-Sequence](https://github.com/wisdompeak/LeetCode/tree/master/DFS/1718.Construct-the-Lexicographically-Largest-Valid-Sequence) (H-) 
 [1723.Find-Minimum-Time-to-Finish-All-Jobs](https://github.com/wisdompeak/LeetCode/tree/master/Dynamic_Programming/1723.Find-Minimum-Time-to-Finish-All-Jobs) (H-) 
-[1766.Tree-of-Coprimes](https://github.com/wisdompeak/LeetCode/tree/master/DFS/1766.Tree-of-Coprimes) (H) 
+[1766.Tree-of-Coprimes](https://github.com/wisdompeak/LeetCode/tree/master/DFS/1766.Tree-of-Coprimes) (H-) 
 * ``search in an array`` 
 [301.Remove-Invalid-Parentheses](https://github.com/wisdompeak/LeetCode/tree/master/DFS/301.Remove-Invalid-Parentheses) (H) 
 [473.Matchsticks-to-Square](https://github.com/wisdompeak/LeetCode/tree/master/DFS/473.Matchsticks-to-Square) (M+)