Lee Sedol Beats AlphaGo in Game 4
Relevant tweets from Demis;    Lee Sedol is playing brilliantly! #AlphaGo thought it
    was doing well, but got confused on move 87. We
    are in trouble now...

    Mistake was on move 79, but #AlphaGo only came to
    that realisation on around move 87

    When I say 'thought' and 'realisation' I just mean the
    output of #AlphaGo value net. It was around 70% at
    move 79 and then dived on move 87

    Lee Sedol wins game 4!!! Congratulations! He was
    too good for us today and pressured #AlphaGo into
    a mistake that it couldn’t recover from

From: https://twitter.com/demishassabis