def longest_palindrome(s):
    # Transform s into T with special characters
    T = '#'.join('^{}$'.format(s))
    n = len(T)
    P = [0] * n
    C = R = 0
    max_len = 0

    for i in range(1, n - 1):
        # Find the mirror of the current index
        mirror = 2 * C - i

        # Check if the current index is within the right boundary
        if i < R:
            P[i] = min(R - i, P[mirror])

        # Attempt to expand palindrome centered at i
        while T[i + P[i] + 1] == T[i - P[i] - 1]:
            P[i] += 1

        # Update the center and right boundary if the palindrome expands past R
        if i + P[i] > R:
            C, R = i, i + P[i]

        # Update the maximum length found
        if P[i] > max_len:
            max_len = P[i]

    return max_len

s = input().strip()
n = len(s)
if n == 0:
    print(0)
else:
    L = longest_palindrome(s)
    if L == n:
        print(L - 1)
    else:
        print(L)