#include <bits/stdc++.h>
using namespace std;
const long long int N = (1ll << 20), mod = 1000000007, bit = 60;
long long int dp[N];
signed main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
  long long int pro = 1, temp, t, i, j, l, r, n, m, mid, z, k, x, y, rem,
                carry = 0, ind, ans = 0, mx = -LONG_LONG_MAX,
                mn = LONG_LONG_MAX, cnt = 0, curr = 0, prev, next, sum = 0,
                flag = 1, i1 = -1, i2 = -1, u, v;
  string s;
  cin >> s;
  n = s.length();
  for (i = 0; i < n; i++) {
    long long int mask = 0;
    for (j = i; j < n; j++) {
      x = s[j] - 'a';
      if (mask & (1ll << x)) {
        break;
      }
      mask |= (1ll << x);
      dp[mask] = j - i + 1;
    }
  }
  for (i = 0; i < 20; i++) {
    for (long long int mask = 0; mask < (1ll << 20); mask++) {
      if (mask & (1ll << i)) {
        dp[mask] = max(dp[mask], dp[mask ^ (1ll << i)]);
      }
    }
  }
  for (i = 0; i < (1ll << 20); i++) {
    ans = max(ans, dp[i] + dp[((1ll << 20) - 1) ^ i]);
  }
  cout << ans << '\n';
  return 0;
}
