s = input().strip()

# Function to check if the string is a palindrome
def is_palindrome(s):
    return s == s[::-1]

if not is_palindrome(s):
    print(len(s))
else:
    # Check if all characters are the same
    all_same = all(c == s[0] for c in s)
    if all_same:
        if len(s) % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        if len(s) == 1:
            print(-1)
        else:
            print(len(s) - 2)