24 соседние различные

s = open('24_demo.txt').readline()
l = 0
r = 0
answ = 1
while r + 1 < len(s):
    if s[r] != s[r + 1]:
        r += 1
        answ = max(answ, r - l + 1)
    else:
        r += 1
        l = r
print(answ)