Update README.md

Author: rezwanh001

README.md

@@ -31,3 +31,7 @@ This repository contains python programming with data structures and algorithms.
             - [Solution](https://github.com/rezwanulhaquerezwan/python-programming-with-data-structures-and-algorithms/blob/master/A.%20Theatre%20Square.py)
         - [A. Watermelon](http://codeforces.com/problemset/problem/4/A)
             - [Solution](https://github.com/rezwanulhaquerezwan/python-programming-with-data-structures-and-algorithms/blob/master/A.%20Watermelon.py)
+            
+    - [AtCoder](http://atcoder.jp/)
+        - [B - Two Switches](http://abc070.contest.atcoder.jp/tasks/abc070_b)
+            - [Solution]()