S = input()

l = len(S)

f = 0
for i in range(l):
    if S[i] != S[l-1-i]:
        f = 1
        break

if f == 1:
    print(l)
else:
    if l == 3:
        print(-1)
    elif S.count(S[0]) == l:
        if l % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        print(l-2)