def is_palindrome(s):
    return s == s[::-1]

S = input().strip()

if not is_palindrome(S):
    print(len(S))
else:
    all_same = all(c == S[0] for c in S)
    if all_same:
        if len(S) % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        print(len(S) - 2)