function x=hailstone(n)
    // iterative definition
    // usage: global verbose; verbose=%T; hailstone(27)
    global verbose
    x=0; loop=%T
    while(loop)
        x=x+1
        if verbose then
            printf('%i ',n)
        end
        if n==1 then
            loop=%F
        elseif modulo(n,2)==1 then
            n=3*n+1
        else
            n=n/2
        end
    end
endfunction

global verbose;
verbose=1;
N=hailstone(27);
printf('\n\n%i\n',N);

global verbose;
verbose=0;
N=100000;
M=zeros(N,1);
for k=1:N
  M(k)=hailstone(k);
end;
[maxLength,n]=max(M)