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"

  Constraints:

0 <= s.length <= 1000
t.length == s.length + 1
s and t consist of lowercase English letters.