function [R,err,lambda_n] = implQR_shift_defl(A,m)
% explicit QR-algorithm
%   Input:  A - matrix
%           m - number of iterations
%   Output: R - upper triangular matrix
%           err - velikosti prvku A(n,n-1)
%           lambda_n - aproximace nejmensiho vl.c.
R=A;
err = [];
lambda_n = A;

n = size(A,1);
if n == 1
 return;
end
err = [abs(A(n,n-1))];
lambda_n = A(n,n);

for i=1:m,
    A = createbulge(A, lambda_n(end));
    A = bulgechasing(A);
    err = [err,abs(A(n,n-1))];
    if err(end) < 1e-12 % deflace
        [Rin, errIn, lambda_nIn] = implQR_shift(A(1:end-1, 1:end-1),m);
        err = [err, errIn];
        lambda_n = [lambda_n, lambda_nIn];
        A(1:end-1, 1:end-1) = Rin;
        break;
    end
    lambda_n = [lambda_n, A(n,n)];
end

R=A;