S = input().strip()

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

def all_same(s):
    return len(set(s)) == 1

if not is_palindrome(S):
    print(len(S))
else:
    if all_same(S):
        if len(S) % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        print(max(0, len(S) - 2))