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 <= 1000t.length == s.length + 1sandtconsist of lower-case English letters.