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()
s = S[0]
for t in S:
    if t != s:
        break
else:
    if len(S) % 2 == 1:
        print(-1)
    else:
        print(0)
    exit()

N = len(S)
for i in range(N):
    if S[i] != S[N-1-i]:
        print(N)
        break
else:
    if N == 3:
        print(-1)
    else:
        print(N-2)