function [MU,S] = k2mask(K,m,n)
% K must be fully valid!!
MU = {};
S = 0;
for t=1:n
  S = S + sum(K.*(K>0));  
  kseg = K(1:m);
  mu = find(kseg>0);
  MU{end+1} = mu;
  K = getK1(K,m,n-t+1);
end
return