iterations=10000;
wins = zeros(1, 3);
for i=1:iterations
    if rand < 0.5
        winner = 1;
        loser = 2;
    else
        winner = 2;
        loser = 1;
    end

    while 1
        contender = 6 - (winner + loser);
        if rand < 0.5
            wins(winner) = wins(winner) + 1;
            break
        else
            loser = winner;
            winner = contender;
        end
    end
end

win_percentage = 100*wins/iterations;