function n=Nb()
%Nb produces a single simulation of the random variable N
%
n=0;                    %Initialize
d=randi(6,[1,1]);
while not(d==1 || d==2) %Repeatedly sample until finding a 1 or 2
   n=n+1;               %n is #rolls when 1 or 2 was found
   d=randi(6,[1,1]);
end