diff --git a/README.md b/README.md
index d07e6ea..4061385 100644
--- a/README.md
+++ b/README.md
@@ -19,3 +19,4 @@ Problem | Concepts/Algorithms Used | Complexity | Solution
 10| Arrays / Pairs / Hash Map | O(n) | [S10](Solutions/S10.cpp) |
 11| Depth First Search (DFS) | O(n) | [S11](Solutions/S11.cpp) |
 12| Arrays | O(n) | [S12](Solutions/S12.cpp) |
+13| Strings, Number Theory | O(nk) (k -> Number of digits to remove) | [S13](Solutions/S13.cpp) |