Задание №73620 ЕГЭ Информатике

f = open("24.txt").readline()
f = f.replace('A','A ').replace('B','B ').split(' ')
maxi = 0
for i in range(len(f)-2):
    c = f[i] + f[i+1]+ f[i+2][:-1]
    if c.count('A') == 1 and c.count('B') == 1:
        maxi= max(maxi, len(c))
c = f[-3] + f[-2]+ f[-1]
if c.count('A') == 1 and c.count('B') == 1:
    maxi= max(maxi, len(c))
print(maxi)