Find the Difference

from collections import Counter

class Solution:
    def findTheDifference(self, s: str, t: str) -> str:
        src = dict(Counter(s))
        tgt = dict(Counter(t))

        for k, v in src.items():
            if tgt[k] - src[k] == 1:
                return k
        
        return list(set(tgt) - set(src))[0]