CF1895C.Torn Lucky Ticket

A ticket is a non-empty string of digits from $1$ to $9$.

A lucky ticket is such a ticket that:

• it has an even length;
• the sum of digits in the first half is equal to the sum of digits in the second half.

You are given $n$ ticket pieces $s_1, s_2, \dots, s_n$. How many pairs $(i, j)$ (for $1 \le i, j \le n$) are there such that $s_i + s_j$ is a lucky ticket? Note that it's possible that $i=j$.

Here, the + operator denotes the concatenation of the two strings. For example, if $s_i$ is 13, and $s_j$ is 37, then $s_i + s_j$ is 1337.

一张票是一个由数字 $1$ 到 $9$ 组成的非空字符串。

一张幸运票是满足以下条件的票：

• 其长度为偶数；
• 前一半数字之和等于后一半数字之和。

给定 $n$ 张票片段 $s_1, s_2, \dots, s_n$。有多少对 $(i, j)$（其中 $1 \le i, j \le n$）满足 $s_i + s_j$ 是一张幸运票？注意，$i = j$ 是允许的。

此处，$+$ 运算符表示两个字符串的拼接。例如，若 $s_i$ 为 13，$s_j$ 为 37，则 $s_i + s_j$ 为 1337。

The first line contains a single integer $n$ ($1 \le n \le 2 \cdot 10^5$) — the number of ticket pieces.

The second line contains $n$ non-empty strings $s_1, s_2, \dots, s_n$, each of length at most $5$ and consisting only of digits from $1$ to $9$.

第一行包含一个整数 $n$（$1 \le n \le 2 \cdot 10^5$）—— 表示车票碎片的数量。

第二行包含 $n$ 个非空字符串 $s_1, s_2, \dots, s_n$，每个字符串长度至多为 $5$，且仅由数字 $1$ 到 $9$ 组成。

Print a single integer — the number of pairs $(i, j)$ (for $1 \le i, j \le n$) such that $s_i + s_j$ is a lucky ticket.

输出一个整数——满足 $s_i + s_j$ 是幸运车票的数对 $(i, j)$（其中 $1 \le i, j \le n$）的个数。