function h=inv_cdf(a,M)

h(1:M) = 0;
df=cdf(a);
step = 1/M;
p=0;    % =step ??
j=1;
for i=1:M
   if( p<=df(j))
      %do nothing
   elseif( p>df(j) )
      while( p>df(j) )
         j=j+1;
      end
   end
   h(i)= j;
   p=p+step;
end