#include <bits/stdc++.h>
using namespace std;
void preprocess(void) { return; }
int dp[(1 << 20)];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.precision(20);
  preprocess();
  string st;
  cin >> st;
  int n = (int)st.length();
  vector<int> ar;
  memset(dp, 0, sizeof dp);
  for (int i = 0; i < n; i++) {
    int val = 0;
    for (int j = i; j >= 0; j--) {
      int p = (st[j] - 'a');
      if (val & (1 << p)) break;
      val |= (1 << p);
      dp[val] = __builtin_popcount(val);
      ar.push_back(val);
    }
  }
  for (int i = 0; i < 20; i++) {
    for (int j = 0; j < (1 << 20); j++) {
      if (j & (1 << i)) dp[j] = max(dp[j ^ (1 << i)], dp[j]);
    }
  }
  int ans = 0;
  for (int i = 0; i < (int)(ar).size(); i++) {
    int f = ar[i];
    int c1 = __builtin_popcount(f);
    f = ar[i] ^ ((1 << 20) - 1);
    int c2 = dp[f];
    ans = max(ans, c1 + c2);
  }
  cout << ans << endl;
}
