S = input().strip()
n = len(S)

if S == S[::-1]:
    # Check if all characters are the same
    all_same = all(c == S[0] for c in S)
    if all_same:
        if n % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        print(n - 2)
else:
    print(n)