local s = io.read()
local allsame = true
local n = #s
for i = 2, n do
  if s:byte(1) ~= s:byte(i) then
    allsame = false break
  end
end
local pali = true
for i = 1, n do
  local j = n + 1 - i
  if i < j then
    if s:byte(i) ~= s:byte(j) then pali = false break end
  else
    break
  end
end
if allsame then
  print(n % 2 == 0 and 0 or -1)
else
  if pali then
    print(n == 3 and -1 or n - 2)
  else
    print(n)
  end
end