s = list(str(input()))
n = len(s)
flag = True
for i in range(n//2):
    if s[i] != s[n-1-i]:
        flag = False
        break
if not flag:
    print(n)
    exit()
if len(set(s)) == 1:
    if n%2 == 1:
        print(-1)
    else:
        print(0)
else:
    if n == 3:
        print(-1)
    else:
        print(n-2)