S = list(input())
N = len(S)
left, right = 0, N - 1
while left < right:
    if S[left] != S[right]:
        print(N)
        exit()
    left += 1
    right -= 1
if len(set(S)) == 1:
    if len(S) % 2:
        print(-1)
    else:
        print(0)
else:
    if len(S) == 3 and S[0] == S[-1]:
        print(-1)
    else:
        print(N - 2)