389\. Find the Difference

Easy

You are given two strings `s` and `t`.

String `t` is generated by random shuffling string `s` and then add one more letter at a random position.

Return the letter that was added to `t`.

**Example 1:**

**Input:** s = "abcd", t = "abcde"

**Output:** "e"

**Explanation:** 'e' is the letter that was added.

**Example 2:**

**Input:** s = "", t = "y"

**Output:** "y"

**Example 3:**

**Input:** s = "a", t = "aa"

**Output:** "a"

**Example 4:**

**Input:** s = "ae", t = "aea"

**Output:** "a"

**Constraints:**

*   `0 <= s.length <= 1000`
*   `t.length == s.length + 1`
*   `s` and `t` consist of lower-case English letters.