#include <bits/stdc++.h>
using namespace std;
const int N = 100010;
int inf = 1e9;
int mod = 1e9 + 7;
const int M = 20;
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  int n = (int)s.length();
  int dp[(1 << M)];
  memset(dp, 0, sizeof(dp));
  int maxi = 0;
  for (int i = 0; i < n; i++) {
    int mask = 0;
    int cnt = 0;
    for (int j = i; j < n; j++) {
      int x = s[j] - 'a';
      if ((mask >> x) & 1) {
        break;
      }
      mask ^= (1 << x);
      cnt++;
      dp[mask] = cnt;
    }
    maxi = max(maxi, cnt);
  }
  for (int i = 0; i < M; i++) {
    for (int j = 0; j < (1 << M); j++) {
      if (j & (1 << i)) {
        dp[j] = max(dp[j], dp[j ^ (1 << i)]);
      }
    }
  }
  for (int i = 0; i < (1 << M); i++) {
    int comp = (1 << M) - 1 - i;
    maxi = max(maxi, dp[i] + dp[comp]);
  }
  cout << maxi << "\n";
  return 0;
}
