#include <bits/stdc++.h>
using namespace std;
template <class T1, class T2>
bool chmin(T1 &a, T2 b) {
  return b < a && (a = b, true);
}
template <class T1, class T2>
bool chmax(T1 &a, T2 b) {
  return a < b && (a = b, true);
}
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using P = pair<ll, ll>;
using ld = long double;
using vld = vector<ld>;
using vi = vector<int>;
using vvi = vector<vi>;
vll conv(vi &v) {
  vll r(v.size());
  for (long long i = 0; i < (long long)(v.size()); i++) r[i] = v[i];
  return r;
}
inline void input(int &v) {
  v = 0;
  char c = 0;
  int p = 1;
  while (c < '0' || c > '9') {
    if (c == '-') p = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    v = (v << 3) + (v << 1) + c - '0';
    c = getchar();
  }
  v *= p;
}
template <typename T, typename U>
ostream &operator<<(ostream &o, const pair<T, U> &v) {
  o << "(" << v.first << ", " << v.second << ")";
  return o;
}
template <size_t...>
struct seq {};
template <size_t N, size_t... Is>
struct gen_seq : gen_seq<N - 1, N - 1, Is...> {};
template <size_t... Is>
struct gen_seq<0, Is...> : seq<Is...> {};
template <class Ch, class Tr, class Tuple, size_t... Is>
void print_tuple(basic_ostream<Ch, Tr> &os, Tuple const &t, seq<Is...>) {
  using s = int[];
  (void)s{0, (void(os << (Is == 0 ? "" : ", ") << get<Is>(t)), 0)...};
}
template <class Ch, class Tr, class... Args>
auto operator<<(basic_ostream<Ch, Tr> &os, tuple<Args...> const &t)
    -> basic_ostream<Ch, Tr> & {
  os << "(";
  print_tuple(os, t, gen_seq<sizeof...(Args)>());
  return os << ")";
}
ostream &operator<<(ostream &o, const vvll &v) {
  for (long long i = 0; i < (long long)(v.size()); i++) {
    for (long long j = 0; j < (long long)(v[i].size()); j++)
      o << v[i][j] << " ";
    o << endl;
  }
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<T> &v) {
  o << '[';
  for (long long i = 0; i < (long long)(v.size()); i++)
    o << v[i] << (i != v.size() - 1 ? ", " : "");
  o << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const set<T> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++)
    o << *it << (next(it) != m.end() ? ", " : "");
  o << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const unordered_set<T> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++)
    o << *it << (next(it) != m.end() ? ", " : "");
  o << "]";
  return o;
}
template <typename T, typename U>
ostream &operator<<(ostream &o, const map<T, U> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++)
    o << *it << (next(it) != m.end() ? ", " : "");
  o << "]";
  return o;
}
template <typename T, typename U, typename V>
ostream &operator<<(ostream &o, const unordered_map<T, U, V> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++) o << *it;
  o << "]";
  return o;
}
vector<int> range(const int x, const int y) {
  vector<int> v(y - x + 1);
  iota(v.begin(), v.end(), x);
  return v;
}
template <typename T>
istream &operator>>(istream &i, vector<T> &o) {
  for (long long j = 0; j < (long long)(o.size()); j++) i >> o[j];
  return i;
}
string bits_to_string(ll input, ll n = 64) {
  string s;
  for (long long i = 0; i < (long long)(n); i++)
    s += '0' + !!(input & (1ll << i));
  reverse((s).begin(), (s).end());
  return s;
}
template <typename T>
ostream &operator<<(ostream &o, const priority_queue<T> &v) {
  auto tmp = v;
  while (tmp.size()) {
    auto x = tmp.top();
    tmp.pop();
    o << x << " ";
  }
  o << endl;
  return o;
}
template <typename T>
unordered_map<T, ll> counter(vector<T> vec) {
  unordered_map<T, ll> ret;
  for (auto &&x : vec) ret[x]++;
  return ret;
};
string substr(string s, P x) { return s.substr(x.first, x.second - x.first); }
void vizGraph(vvll &g, int mode = 0, string filename = "out.png") {
  ofstream ofs("./out.dot");
  ofs << "digraph graph_name {" << endl;
  set<P> memo;
  for (long long i = 0; i < (long long)(g.size()); i++)
    for (long long j = 0; j < (long long)(g[i].size()); j++) {
      if (mode && (memo.count(P(i, g[i][j])) || memo.count(P(g[i][j], i))))
        continue;
      memo.insert(P(i, g[i][j]));
      ofs << "    " << i << " -> " << g[i][j]
          << (mode ? " [arrowhead = none]" : "") << endl;
    }
  ofs << "}" << endl;
  ofs.close();
  system(((string) "dot -T png out.dot >" + filename).c_str());
}
size_t random_seed;
namespace std {
using argument_type = P;
template <>
struct hash<argument_type> {
  size_t operator()(argument_type const &x) const {
    size_t seed = random_seed;
    seed ^= hash<ll>{}(x.first);
    seed ^= (hash<ll>{}(x.second) << 1);
    return seed;
  }
};
};  // namespace std
namespace myhash {
const int Bsizes[] = {3,  9,  13, 17, 21, 25, 29, 33, 37, 41,
                      45, 49, 53, 57, 61, 65, 69, 73, 77, 81};
const int xor_nums[] = {0x100007d1, 0x5ff049c9, 0x14560859, 0x07087fef,
                        0x3e277d49, 0x4dba1f17, 0x709c5988, 0x05904258,
                        0x1aa71872, 0x238819b3, 0x7b002bb7, 0x1cf91302,
                        0x0012290a, 0x1083576b, 0x76473e49, 0x3d86295b,
                        0x20536814, 0x08634f4d, 0x115405e8, 0x0e6359f2};
const int hash_key = xor_nums[rand() % 20];
const int mod_key = xor_nums[rand() % 20];
template <typename T>
struct myhash {
  std::size_t operator()(const T &val) const {
    return (hash<T>{}(val) % mod_key) ^ hash_key;
  }
};
};  // namespace myhash
template <typename T>
class uset : public std::unordered_set<T, myhash::myhash<T>> {
  using SET = std::unordered_set<T, myhash::myhash<T>>;

 public:
  uset() : SET() { SET::rehash(myhash::Bsizes[rand() % 20]); }
};
uint32_t randxor() {
  static uint32_t x = 1 + (uint32_t)random_seed, y = 362436069, z = 521288629,
                  w = 88675123;
  uint32_t t;
  t = (x ^ (x << 11));
  x = y;
  y = z;
  z = w;
  return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}
struct timeval start;
double sec() {
  struct timeval tv;
  gettimeofday(&tv, NULL);
  return (tv.tv_sec - start.tv_sec) + (tv.tv_usec - start.tv_usec) * 1e-6;
}
struct init_ {
  init_() {
    gettimeofday(&start, NULL);
    ios::sync_with_stdio(false);
    cin.tie(0);
    struct timeval myTime;
    struct tm *time_st;
    gettimeofday(&myTime, NULL);
    time_st = localtime(&myTime.tv_sec);
    srand(myTime.tv_usec);
    random_seed = RAND_MAX / 2 + rand() / 2;
  }
} init__;
static const double EPS = 1e-14;
static const long long INF = 1e18;
static const long long mo = 1e9 + 7;
ll flip(ll mask, ll i) {
  if (mask & (1ll << i)) {
    mask = (~mask) | (1ll << i);
    mask = ~mask;
  } else {
    mask |= (1ll << i);
  }
  return mask;
}
const ll w = 26;
ll solveDP(string s, bool fast = 1) {
  ll n = s.length();
  if (n <= 1) {
    return 1;
  }
  vvll a(w, vll(n + 1));
  for (long long c = 0; c < (long long)(w); c++) {
    for (long long i = 0; i < (long long)(n); i++) {
      a[c][i + 1] = a[c][i] + (s[i] == 'a' + c);
    }
  }
  unordered_map<int, int> memo;
  vll masks(n + 1);
  ll mask = 0;
  memo[mask] = 0;
  for (long long i = 0; i < (long long)(n); i++) {
    mask = flip(mask, s[i] - 'a');
    masks[i + 1] = mask;
    if (!memo.count(mask)) {
      memo[mask] = i + 1;
    }
  }
  vll dp(n + 1, INF);
  dp[0] = 0;
  for (long long i = (long long)(1); i < (long long)(n + 1); i++) {
    ll mask = masks[i];
    if (memo.count(mask)) {
      ll prev = memo[mask];
      if (prev < i) {
        chmin(dp[i], dp[prev] + 1);
      }
    }
    for (long long c = 0; c < (long long)(w); c++) {
      ll new_mask = flip(mask, c);
      if (memo.count(new_mask)) {
        ll prev = memo[new_mask];
        if (prev < i) {
          chmin(dp[i], dp[prev] + 1);
        }
      }
    }
  }
  return dp[n];
}
ll solve(string s, ll fast = 1) {
  if (fast) {
    string t;
    for (long long i = 0; i < (long long)(s.length()); i++) {
      if (s[i] == s[i + 1]) {
        i++;
      } else {
        t += s[i];
      }
    }
    swap(s, t);
  }
  ll n = s.length();
  if (n <= 1) {
    return 1;
  }
  vvll a(w, vll(n + 1));
  for (long long c = 0; c < (long long)(w); c++) {
    for (long long i = 0; i < (long long)(n); i++) {
      a[c][i + 1] = a[c][i] + (s[i] == 'a' + c);
    }
  }
  vll dp(n + 1, INF);
  vll A(n + 1, INF);
  vvll test(n + 1, vll(n + 1, 2));
  dp[0] = 0;
  for (long long i = (long long)(1); i < (long long)(n + 1); i++) {
    for (long long j = 0; j < (long long)(i); j++) {
      ll counter = 0;
      for (long long c = 0; c < (long long)(w); c++) {
        counter += (a[c][i] - a[c][j]) % 2 == 1;
      }
      ll f = 0;
      if (counter > 1) {
        test[i][j] = 0;
        f = 1;
      } else {
        test[i][j] = 1;
      }
      if (f) continue;
      if (dp[i] > dp[j] + 1) {
        A[i] = j;
        dp[i] = dp[j] + 1;
      }
    }
  }
  return dp[n];
}
int main(void) {
  string s;
  cin >> s;
  ll dp = solveDP(s);
  cout << dp << endl;
  return 0;
}
