from collections import Counter
s = list(input())
c = Counter(s)
if len(c) == 1:
    if len(s) & 1:
        print(-1)
    else:
        print(0)
elif s != s[::-1]:
    print(len(s))
else:
    if len(s) == 3:
        print(-1)
    else:
        print(len(s)-2)