function [RICs, RIC] = get_ric(A, K)
    sample_times = 500;
    [m, n] = size(A);
    RICs = zeros(2 * sample_times, 1);

    for i = 1: sample_times
        indices = randperm(n, K);
        A_Lambda = A(:, indices(:));
        B = conj(A_Lambda') * A_Lambda;
        eig_B = real(eig(B));
        RICs(2 * i - 1) = min(eig_B) - 1;
        RICs(2 * i) = max(eig_B) - 1;
    end

    RIC = max(RICs);
end