#include <bits/stdc++.h>
template <typename T>
void MACRO_VAR_Scan(T& t) {
  std::cin >> t;
}
template <typename First, typename... Rest>
void MACRO_VAR_Scan(First& first, Rest&... rest) {
  std::cin >> first;
  MACRO_VAR_Scan(rest...);
}
template <typename T>
void MACRO_VEC_ROW_Init(int n, T& t) {
  t.resize(n);
}
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Init(int n, First& first, Rest&... rest) {
  first.resize(n);
  MACRO_VEC_ROW_Init(n, rest...);
}
template <typename T>
void MACRO_VEC_ROW_Scan(int p, T& t) {
  std::cin >> t[p];
}
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Scan(int p, First& first, Rest&... rest) {
  std::cin >> first[p];
  MACRO_VEC_ROW_Scan(p, rest...);
}
template <typename T>
inline T CHMAX(T& a, const T b) {
  return a = (a < b) ? b : a;
}
template <typename T>
inline T CHMIN(T& a, const T b) {
  return a = (a > b) ? b : a;
}
void CHECKTIME(std::function<void()> f) {
  auto start = std::chrono::system_clock::now();
  f();
  auto end = std::chrono::system_clock::now();
  auto res = std::chrono::duration_cast<std::chrono::nanoseconds>((end - start))
                 .count();
  std::cerr << "[Time:" << res << "ns  (" << res / (1.0e9) << "s)]\n";
}
template <class T>
std::vector<std::vector<T>> VV(int n) {
  return std::vector<std::vector<T>>(n);
}
template <class T>
std::vector<std::vector<T>> VV(int n, int m, T init = T()) {
  return std::vector<std::vector<T>>(n, std::vector<T>(m, init));
}
template <typename S, typename T>
std::ostream& operator<<(std::ostream& os, std::pair<S, T> p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using PAIR = std::pair<ll, ll>;
using PAIRLL = std::pair<ll, ll>;
constexpr ll INFINT = 1 << 30;
constexpr ll INFINT_LIM = (1LL << 31) - 1;
constexpr ll INFLL = 1LL << 60;
constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62);
constexpr double EPS = 1e-9;
constexpr ll MOD = 1000000007;
constexpr double PI = 3.141592653589793238462643383279;
std::string s;
std::map<ll, std::map<ll, ll>> map;
ll calc(ll l, ll r) {
  if (l >= r) return 0;
  if (map.count(l) && map[l].count(r)) return map[l][r];
  std::set<char> set;
  std::vector<ll> lt, rt;
  for (ll i = (l); i < (r); ++i) {
    if (set.count(s[i]))
      set.erase(s[i]);
    else
      set.insert(s[i]);
    if (set.size() <= 1) lt.emplace_back(i + 1);
  }
  if (lt.back() == r) return 1;
  set.clear();
  for (ll i = (r)-1; i >= (l); --i) {
    if (set.count(s[i]))
      set.erase(s[i]);
    else
      set.insert(s[i]);
    if (set.size() <= 1) rt.emplace_back(i);
  }
  if (lt.size() == 1 || rt.size() == 1) {
    map[l][r] = calc(lt.back(), rt.back()) + 2;
  } else {
    {
      ll t = lt.back();
      ll mi;
      for (auto x : rt) {
        if (t <= x) CHMIN(mi, x);
      }
      CHMAX(map[l][r], calc(t, mi) + 2);
    }
    {
      ll t = rt.back();
      ll ma;
      for (auto x : lt) {
        if (x <= t) CHMAX(ma, x);
      }
      CHMAX(map[l][r], calc(ma, t) + 2);
    }
  }
  return map[l][r];
}
signed main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  ;
  std::cin >> s;
  std::cout << calc(0, s.size());
  std::cout << "\n";
  ;
  return 0;
}
