def longest_palindrome(s):
    n = len(s)
    i = 0
    j = 0
    rad = [0 for i in range(2 * n)]
    while i < 2 * n:
        while i - j >= 0 and i + j + 1 < 2 * n and s[(i - j) // 2] == s[(i + j + 1) // 2]:
            j += 1
        rad[i] = j
        k = 1
        while i - k >= 0 and rad[i] - k >= 0 and rad[i - k] != rad[i] - k:
            rad[i + k] = min(rad[i - k], rad[i] - k)
            k += 1
        i += k
        j = max(j - k, 0)
    print(max(rad))
#     max_rad = 0
#     max_i = 0
#     for i in range(2 * n):
#         if rad[i] > max_rad:
#             max_rad = rad[i]
#             max_i = i
#     return S[(max_i + 1 - max_rad) // 2: (max_i + 1 + max_rad) // 2]

S = input()
N = len(S)
if S == S[::-1]:
    longest_palindrome(S[1:])
else:
    longest_palindrome(S)
# l = len(longest_palindrome(S))
# if l == N:
#     print(len(longest_palindrome(S[1:])))
# else:
#     print(l)