#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e2 + 10;
const int maxn = (1 << 20);
string str;
int dp[maxn], n;
string tobin(int x) {
  string a;
  if (x == 0) a += '0';
  while (x) {
    if (x % 2)
      a += '1';
    else
      a += '0';
    x /= 2;
  }
  reverse(a.begin(), a.end());
  return a;
}
int solve() {
  for (int i = 0; i < n; i++) {
    int mask = 0;
    for (int j = i; j < min(n, i + 20) && !(mask & (1 << (str[j] - 97))); j++) {
      int bit = str[j] - 97;
      mask |= (1 << bit);
      dp[mask] = __builtin_popcount(mask);
    }
  }
  for (int m = 0; m < maxn; m++) {
    for (int j = 0; j < 20; j++) {
      if (m & (1 << j)) {
        dp[m] = max(dp[m], dp[m ^ (1 << j)]);
      }
    }
  }
  int ans = 0;
  for (int i = 0; i < n; i++) {
    int mask = 0;
    for (int j = i; j < min(n, i + 20) && !(mask & (1 << (str[j] - 97))); j++) {
      int bit = str[j] - 97;
      mask |= (1 << bit);
      int comp = (mask ^ (maxn - 1));
      ans = max(ans, __builtin_popcount(mask) + dp[comp]);
    }
  }
  return ans;
}
int main() {
  cin >> str;
  n = str.size();
  cout << solve() << '\n';
  return 0;
}
