def max(a,b); a > b ? a : b; end
S = gets.chomp
N = S.size
dp = Array.new(N + 1){ Array.new(N + 1, 0) }
ans = 0

(1 .. N).each do |d|
  N.times do |l|
    r = l + d
    break if r > N

    if S[l - 1] == S[r - 2]
      dp[l][r] = dp[l + 1][r - 1] + (l == r - 1 ? 1 : 2)
    else
      dp[l][r] = dp[l + 1][r - 1]
    end
    ans = max(ans, dp[l][r])
  end
end
puts ans