function [L,U] = LUrazcep_trid(Z,D,S, n)
    for k=1:n-1      
       S(k) = S(k)/D(k);
       D(k+1) = D(k+1) - S(k)*Z(k);
    end
    
    U.Z = Z;
    U.D = D;
    
    L.D = ones(1,n);
    L.S = S;
end