s = input()
n = len(s)


a = s[0 : n // 2]
b = s[(n + 1) // 2 : n][::-1]

if a != b:
    print(n)
elif len(set(list(a))) != 1:
    print(n - 2)
elif n % 2 == 1:
    if n == 3:
        print(-1)
    else:
        print(n - 2)
else:
    print(0)