CF1144E.Median String

You are given two strings $s$ and $t$, both consisting of exactly $k$ lowercase Latin letters, $s$ is lexicographically less than $t$.

Let's consider list of all strings consisting of exactly $k$ lowercase Latin letters, lexicographically not less than $s$ and not greater than $t$ (including $s$ and $t$) in lexicographical order. For example, for $k=2$, $s=$"az" and $t=$"bf" the list will be ["az", "ba", "bb", "bc", "bd", "be", "bf"].

Your task is to print the median (the middle element) of this list. For the example above this will be "bc".

It is guaranteed that there is an odd number of strings lexicographically not less than $s$ and not greater than $t$.

给你两个字符串 $s$ 和 $t$，它们均由恰好 $k$ 个小写拉丁字母组成，且 $s$ 在字典序上严格小于 $t$。

考虑所有由恰好 $k$ 个小写拉丁字母组成的字符串构成的列表，这些字符串在字典序上不小于 $s$ 且不大于 $t$（包含 $s$ 和 $t$），并按字典序升序排列。例如，当 $k=2$、$s=$"az"、$t=$"bf" 时，该列表为 ["az", "ba", "bb", "bc", "bd", "be", "bf"]。

你的任务是输出该列表的中位数（即中间那个元素）。对上述例子而言，答案为 "bc"。

题目保证：字典序不小于 $s$ 且不大于 $t$ 的字符串个数为奇数。

The first line of the input contains one integer $k$ ($1 \le k \le 2 \cdot 10^5$) — the length of strings.

The second line of the input contains one string $s$ consisting of exactly $k$ lowercase Latin letters.

The third line of the input contains one string $t$ consisting of exactly $k$ lowercase Latin letters.

It is guaranteed that $s$ is lexicographically less than $t$.

It is guaranteed that there is an odd number of strings lexicographically not less than $s$ and not greater than $t$.

输入的第一行包含一个整数 $k$（$1 \le k \le 2 \cdot 10^5$）—— 字符串的长度。

输入的第二行包含一个字符串 $s$，该字符串恰好由 $k$ 个小写拉丁字母组成。

输入的第三行包含一个字符串 $t$，该字符串恰好由 $k$ 个小写拉丁字母组成。

保证 $s$ 的字典序严格小于 $t$。

保证字典序不小于 $s$ 且不大于 $t$ 的字符串个数为奇数。

Print one string consisting exactly of $k$ lowercase Latin letters — the median (the middle element) of list of strings of length $k$ lexicographically not less than $s$ and not greater than $t$.

输出一个恰好由 $k$ 个小写拉丁字母组成的字符串——即所有长度为 $k$、字典序不小于 $s$ 且不大于 $t$ 的字符串所构成的列表中的中位数（中间元素）。