#include <bits/stdc++.h>
using namespace std;
const long long max_mask = (1 << 20);
long long n, cnt, mask, dp[max_mask];
string s;
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> s;
  s = '0' + s;
  for (long long l = 1; l < s.length(); l++) {
    mask = 0;
    cnt = 0;
    long long r = l;
    while (r < s.length() && ((mask & (1 << (s[r] - 'a'))) == 0)) {
      mask = mask | (1 << (s[r] - 'a'));
      cnt++;
      dp[mask] = cnt;
      r++;
    }
  }
  for (long long cur_mask = 0; cur_mask < max_mask; cur_mask++) {
    for (long long lett_to_add = 0; lett_to_add < 20; lett_to_add++) {
      if ((cur_mask & (1 << lett_to_add)) == 0) {
        long long new_mask = cur_mask | (1 << lett_to_add);
        dp[new_mask] = max(dp[cur_mask], dp[new_mask]);
      }
    }
  }
  long long ans = 0;
  for (long long cur_mask = 0; cur_mask < max_mask; cur_mask++) {
    long long comp = max_mask - 1 - cur_mask;
    ans = max(ans, dp[cur_mask] + dp[comp]);
  }
  cout << ans << endl;
  return 0;
}
