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

# Check if the string is a palindrome
is_palindrome = True
for i in range(n // 2):
    if s[i] != s[n - 1 - i]:
        is_palindrome = False
        break

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