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

def all_same(s):
    return all(c == s[0] for c in s)

S = input().strip()
n = len(S)

if not is_palindrome(S):
    print(n)
else:
    if all_same(S):
        if n % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        if n >= 2:
            print(n - 2)
        else:
            print(-1 if n == 1 else 0)