S = list(input())
N = len(S)

s = set(S)

if len(s) == 1:
    if len(S) % 2 == 1:
        print (-1)
    else:
        print (0)
else:

    flag = True
    for i in range(N):

        if S[i] != S[len(S)-1-i]:
            flag = False

    if not flag:
        print (len(S))
    else:
        print (len(S)-2)