from collections import Counter

S = str(input())
N = len(S)
if N == 1:
  print(-1)
  exit()
ls = list(S)
cs = Counter(ls)
if len(cs) == 1:
  if N%2 == 0:
    print(0)
  else:
    print(-1)
else:
  if S[:N//2] != S[N-1:N//2:-1]:
    print(N)
  else:
    if N == 3:
      print(-1)
    else:
      print(N-2)