mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    S = input().rstrip('\n')

    if len(set(S)) == 1:
        if len(S) & 1:
            print(-1)
        else:
            print(0)
        exit()

    if len(S) & 1:
        if S != S[::-1]:
            print(len(S))
        else:
            if len(S) == 3:
                print(-1)
            else:
                print(len(S) - 2)
    else:
        if S == S[::-1]:
            print(len(S) - 2)
        else:
            print(len(S))


if __name__ == '__main__':
    main()