S = input()
N = len(S)
Flag = 0
for i in range(N // 2):
    j = N - i - 1
    if S[i] != S[j]:
        print(N)
        exit()
    if S[0] != S[i]: Flag = 1
if Flag: print(N - 2)
elif N % 2 == 0: print(0)
elif S[0] == S[N // 2]: print(-1)
elif N == 3: print(-1)
else: print(N - 2)