     "source": [
      "import sys\n",
      "\n",
      "\n",
      "class MyStack(Stack):\n",
      "\n",
      "    def __init__(self, top=None):\n",
      "        # TODO: Implement me\n",
      "        pass\n",
      "\n",
 
</s> remove     "class MyStack(Stack):\n",
 </s> add     "class StackMin(Stack):\n", </s> remove     "        super(MyStack, self).__init__(top)\n",
 </s> add  </s> remove     "        stack = MyStack()\n",
 </s> add     "        stack = StackMin()\n", </s> remove     "        stack = MyStack()\n",
 </s> add     "        stack = StackMin()\n",
    "class StackMin(Stack):\n",
     "source": [
      "import sys\n",
      "\n",
      "\n",
    "class StackMin(Stack):\n",
      "\n",
      "    def __init__(self, top=None):\n",
      "        # TODO: Implement me\n",
      "        pass\n",
      "\n",
keep keep keep keep replace keep keep keep keep keep
 Polish stack min challenge and solution (#72)

Update constraints, algorithm discussion, code, and tests. 
stacks_queues/stack_min/stack_min_challenge.ipynb