update README.md

fixed link to unsolved: 21.3.4 24.4.9 32.3.4 32.4.6

README.md

@@ -314,17 +314,17 @@ If a problem is too easy to solve, we'll mark it as **straightforward** in order
 # UNSOLVED
 
 [21.2.5](./C21-Data-Structures-for-Disjoint-Sets/21.2.md#exercises-212-5)
-[21.3.4](./C21-Data-Structures-for-Disjoint-Sets/21.3.md#exercises-213-4)
+[21.3.4](./C21-Data-Structures-for-Disjoint-Sets/21.3.md#exercises-213-4-)
 
-[24.4.9](./C24-Single-Source-Shortest-Paths/24.4.md#exercises-244-9)
+[24.4.9](./C24-Single-Source-Shortest-Paths/24.4.md#exercises-244-9-)
 
 [31.1.11](./C31-Number-Theoretic-Algorithms/31.1.md#exercises-311-11)
 [31.2.7](./C31-Number-Theoretic-Algorithms/31.2.md#exercises-312-7)
 [31.2.9](./C31-Number-Theoretic-Algorithms/31.2.md#exercises-312-9)
 
 [32.2.4](./C32-String-Matching/32.2.md#exercises-322-4)
-[32.3.4](./C32-String-Matching/32.3.md#exercises-323-4)
-[32.4.6](./C32-String-Matching/32.4.md#exercises-324-6)
+[32.3.4](./C32-String-Matching/32.3.md#exercises-323-4-)
+[32.4.6](./C32-String-Matching/32.4.md#exercises-324-6-)
 
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