S = input().strip()

def longest_palindrome(s):
    if not s:
        return 0
    t = '#' + '#'.join(s) + '#'
    n = len(t)
    p = [0] * n
    c = r = 0
    max_len = 0
    for i in range(n):
        mirror = 2 * c - i
        if i < r:
            p[i] = min(r - i, p[mirror])
        a = i + p[i] + 1
        b = i - p[i] - 1
        while a < n and b >= 0 and t[a] == t[b]:
            p[i] += 1
            a += 1
            b -= 1
        if i + p[i] > r:
            c, r = i, i + p[i]
        if p[i] > max_len:
            max_len = p[i]
    return max_len

L = longest_palindrome(S)
if L == len(S):
    print(L - 1)
else:
    print(L)