    },
    "language_info": {
     "codemirror_mode": {
      "name": "ipython",
      "version": 2
     },
     "file_extension": ".py",
     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
 
</s>
    "version": 3
    },
    "language_info": {
     "codemirror_mode": {
      "name": "ipython",
    "version": 3
     },
     "file_extension": ".py",
     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
keep keep keep keep replace keep keep keep keep keep
 Polish queue from stacks challenge and solution (#74)

Update constraints, algorithm discussion, and code.
stacks_queues/queue_from_stacks/queue_from_stacks_solution.ipynb