s = input()
n = len(s)


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

if a != b:
    print(n)
    exit()

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