Update ReadMe.md

Pradyuman7 · web-flow · commit a0bdee9d2db8 · 2019-03-04T04:54:33.000+01:00
diff --git a/Stacks and Queues/ReadMe.md b/Stacks and Queues/ReadMe.md
@@ -7,3 +7,5 @@
 **2. Desgin a stack which can tell the minimum number on the stack in O(1).**
 
 **3. Make a class SetOfStacks that has many fixed length stacks which get switched when items exceed the in-use stack, also implement a method popAt() which pops the item at desired location.**
+
+**4. Implement Queue using two stacks.**
