import collections,sys

S = input()
D = collections.Counter(S)
ND = len(D)
N = len(S)

if N == 1:
    print(-1)
elif N == 2:
    if ND == 1:
        print(0)
    else:
        print(N)
elif N == 3:
    if S[0] == S[2]:
        print(-1)
    else:
        print(3)
else:
    if ND == 1:
        if N % 2 == 0:
            print(0)
        else:
            print(-1)
    elif S[:N//2] == S[:-(-N//2)-1:-1]:
        print(N-2)
    else:
        print(N)