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))
    elif len(S) % 2 == 0:
        print (len(S)-2)
    else:
        om = set(S[:N//2] + S[N//2+1:])
        if len(om) == 1 and N == 3:
            print (-1)
        else:
            print (len(S)-2)