Definition: Given a 'poster' sentence and a corresponding 'response' (often, from Facebook or Reddit)classify the sentiment of the given response into four categories: 1) Positive, 2) Negative, 3) Neutral, and 4) Mixed if it contains both positive and negative.
Input: Poster: Iran has yet to prove it can be trusted. Hassan Rouhani's latest stipulation on a nuclear deal is delusional and arrogant.  Responser: Iran has proven the point that they are not serious negotiating partners. We must walk away from the table at this point and implement stricter sanctions to force a stronger deal.
