#include <bits/stdc++.h>
using namespace std;
const int MAX = 2e5 + 5;
int last[30], in, fn;
int dp[(1 << 23)];
void dfs(int mask, int cnt) {
  if (dp[mask] >= cnt) return;
  dp[mask] = max(dp[mask], cnt);
  for (int i = 0; i < 20; i++) {
    if (!(mask & (1 << i))) dfs(mask | (1 << i), cnt);
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  string cad;
  cin >> cad;
  int n = cad.size();
  cad = " " + cad;
  in = 1;
  fn = 1;
  int ans = 0;
  for (int i = 1; i <= n; i++) {
    if (fn - in + 1 == 21) in++;
    fn = i;
    int v = cad[i] - 'a';
    if (last[v] >= in) {
      in = last[v] + 1;
    }
    last[v] = i;
    int mask = 0;
    for (int j = in; j <= fn; j++) mask |= (1 << (cad[j] - 'a'));
    int cnt = fn - in + 1;
    dfs(mask, cnt);
    ans = max(ans, cnt + dp[((1 << 20) - 1) - mask]);
    for (int j = in; j <= fn; j++) {
      mask ^= (1 << (cad[j] - 'a'));
      cnt--;
      dfs(mask, cnt);
      ans = max(ans, cnt + dp[((1 << 20) - 1) - mask]);
    }
  }
  cout << ans << "\n";
}
