#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const int M = 1200000;
int n, m, k;
char s[M];
int num[M];
int dp[M] = {0};
int main() {
  ios::sync_with_stdio(0);
  m = (1 << 20) - 1;
  cin >> s + 1;
  n = strlen(s + 1);
  for (int i = (1); i <= (n); ++i) num[i] = (1 << (s[i] - 'a'));
  for (int i = (1); i <= (n); ++i) {
    int j = i;
    int now = 0;
    int cnt = 0;
    while (j <= n && !(num[j] & now)) {
      cnt++;
      now |= num[j];
      dp[now] = cnt;
      ++j;
    }
  }
  for (int i = (1); i <= (m); ++i) {
    int x = i;
    while (x) {
      dp[i] = max(dp[i], dp[i ^ (x & (-x))]);
      x -= (x & (-x));
    }
  }
  int ans = 0;
  for (int i = (1); i <= (m); ++i) {
    ans = max(ans, dp[i] + dp[m ^ i]);
  }
  cout << ans << endl;
  return 0;
}
