Sequence of P-adic Integers has Convergent Subsequence/Lemma 2

Theorem
Let $\struct {\Q_p, \norm {\,\cdot\,}_p}$ be the $p$-adic numbers for some prime $p$.

Let $\sequence{x_n}$ be a sequence of $p$-adic integers. Let $\sequence{b_0, b_1, \ldots, b_j}$ be a finite sequence of $p$-adic digits, possibly empty, such that:
 * there exists infinitely many $n \in \N$ such that the canonical expansion of $x_n$ begins with the $p$-adic digits $b_j \, \ldots \, b_1 b_0$

Then there exists a $p$-adic digit $b_{j + 1}$ such that:
 * there exists infinitely many $n \in \N$ such that the canonical expansion of $x_n$ begins with the $p$-adic digits $b_{j+1}b_j \, \ldots \, b_1 b_0$

Case 1
Let there exist $b \in \set{0, 1, \ldots, p - 2}$:
 * there exists infinitely many $n \in \N$ such that the canonical expansion of $x_n$ begins with the $p$-adic digits $b b_j \, \ldots \, b_1 b_0$

Let $b_{j+1} = b$ and the result holds.

Case 2
For all $b \in \set{0, 1, \ldots, p - 2}$:
 * there exists only a finite number of $n \in \N$ such that the canonical expansion of $x_n$ begins with the $p$-adic digits $b b_j \, \ldots \, b_1 b_0$

Let:
 * $N = \max \set{n \in \N : \exists b \in \closedint{0}{p-2} : \text{ the canonical expansion of } x_n \text{ begins with the } p \text{-adic digits } b b_j \, \ldots \, b_1 b_0}$

Let $b_{j+1} = p - 1$.

Hence:
 * $\forall n > N :$ the canonical expansion of $x_n$ begins with the $p$-adic digits $b_{j+1} b_j \, \ldots \, b_1 b_0$

The result follows.