from collections import Counter
class Solution:
def longestPalindrome(self, s: str) -> int:
s_letter_cnt = list(Counter(s).values())
palindrom_cnt, flag = 0, False
for cnt in s_letter_cnt:
if cnt % 2 == 0:
palindrom_cnt += cnt
else:
flag = True
palindrom_cnt += cnt-1
return palindrom_cnt if flag is False else palindrom_cnt+1