class Solution:
def characterReplacement(self, s: str, k: int) -> int:
count = {}
res = 0
l = 0
maxf = 0
for r in range(len(s)):
count[s[r]] = 1 + count.get(s[r], 0)
maxf = max(maxf, count[s[r]])
while (r - l + 1) - maxf > k:
count[s[l]] -= 1
l += 1
res = max(res, r - l + 1)
return res