import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


S = S()
N = len(S)

if len(set(list(S))) == 1:
    if N % 2 == 1:
        ans = -1
    else:
        ans = 0
else:
    for i in range(N):
        if S[i] != S[N-1-i]:
            ans = N
            break
    else:
        if N == 3:
            ans = -1
        else:
            ans = N-2

print(ans)