#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vll = vector<ll>;
using vvi = vector<vi>;
using vvl = vector<vll>;
using vb = vector<bool>;
const int INF = 2e9 + 5;
const ll LLINF = (1LL << 60) + 5;
const int A = 20;
const int MUSK = 1 << A;
int main() {
  cin.tie(0), cin.sync_with_stdio(0), cout.tie(0), cout.sync_with_stdio(0);
  string s;
  cin >> s;
  vi v(s.size());
  for (int i = 0; i < s.size(); i++) v[i] = s[i] - 'a';
  vector<bool> elon(MUSK);
  for (int i = 0; i < v.size(); i++) {
    int curr = 0;
    for (int j = 0; i + j < v.size(); j++) {
      if (curr & (1 << v[i + j])) break;
      curr |= (1 << v[i + j]);
      elon[curr] = 1;
    }
  }
  vi dp(MUSK, 0);
  for (int i = 0; i < MUSK; i++) {
    dp[i] = elon[i] ? __builtin_popcount(i) : 0;
    for (int j = 0; j < 20; j++)
      if (i & (1 << j)) dp[i] = max(dp[i], dp[i ^ (1 << j)]);
  }
  int ans = 0;
  for (int i = 0; i < MUSK; i++) {
    if (elon[i]) ans = max(ans, __builtin_popcount(i) + dp[i ^ (MUSK - 1)]);
  }
  cout << ans;
  return cout << endl, 0;
}
