def find_best_start_parameters(x_pocz):
    kp = [-10, -5, -1, 0, 1, 5, 10]
    ki = [-10, -5, -1, 0, 1, 5, 10]
    kd = [-10, -5, -1, 0, 1, 5, 10]

    best_kp = kp[0]
    best_ki = ki[0]
    best_kd = kd[0]

    min_err = model_err((kp[0], ki[0], kd[0]), x_pocz)
    for p in kp:
        for i in ki:
            for d in kd:
                err = model_err((p, i, d), x_pocz)
                if err < min_err:
                    best_kp = p
                    best_ki = i
                    best_kd = d
                    min_err = err

    print('Best start (kp, ki, kd) ' + str(best_kp) + ' ' + str(best_ki) + ' ' + str(best_kd))
    return best_kp, best_ki, best_kd