def solve():
    s = input()
    n = len(s)
    if s != s[::-1]:
        return n
    if n % 2 == 0:
        return 0 if len(set(s)) == 1 else n - 2
    if n == 1:
        return -1
    ss = set(s[:n//2])
    if len(ss) > 1:
        return n - 2
    if n >= 5 and s[n//2] != s[0]:
        return n - 2
    return -1

print(solve())