We can now rewrite Eq. (16) as (aNi−1)MOD(M)=(aNi−1−[Ni−1/q](aq+r))MOD(M), which results in (aNi−1)MOD(M)=(a(Ni−1−[Ni−1/q]q)−[Ni−1/q]r))MOD(M), yielding (aNi−1)MOD(M)=(a(Ni−1MOD(q))−[Ni−1/q]r))MOD(M).