s = input()
n = len(s)

for i in range(n//2):
    if s[i] != s[-i-1]:
        print("{}".format(n))
        exit()

for i in range(n//2-1):
    if (s[i] != s[-i-3]) | (s[i] != s[-i-2]):
        print("{}".format(n-2))
        exit()
    if (s[i+2] != s[-i-1]) | (s[i+1] != s[-i-1]):
        print("{}".format(n-2))
        exit()

ans = -(n % 2)
print("{}".format(ans))