s = input()
n = len(s)

for i in range(n):
    if s[i] != s[n - i - 1]:
        print(n)
        exit()

for i in range(n):
    if n >= 4 and s[i] != s[0]:
        print(n - 2)
        exit()

if n % 2:
    print(-1)
else:
    print(0)