def is_palindrome(s):
    return s == s[::-1]

def solve():
    import sys
    s = sys.stdin.readline().strip()
    n = len(s)
    if n == 0:
        print(-1)
        return
    if not is_palindrome(s):
        print(n)
        return
    # Check if all characters are the same
    first = s[0]
    all_same = True
    for c in s:
        if c != first:
            all_same = False
            break
    if all_same:
        if n % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        print(n - 2)

solve()