#include <bits/stdc++.h>
using namespace std;
const double PI = 3.14159265358979323846;
const double eps = (1e-10);
int isGreater(long double x, long double y) {
  if (abs(x - y) < eps) return 0;
  if (x > y) return 1;
  return -1;
}
const int H = 20;
int F[(1 << H) + 1], mem[(1 << H) + 1];
int inverse(int msk) {
  msk = ~msk;
  msk &= ((1 << H) - 1);
  return msk;
}
int solve(int msk) {
  if (F[msk] != -1) return F[msk];
  int &ret = mem[msk];
  if (~ret) return ret;
  ret = 0;
  for (int i = 0; i < H; ++i) {
    if ((1 << i) & msk) ret = max(ret, solve(msk ^ (1 << i)));
  }
  return ret;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  memset(F, -1, sizeof(F));
  memset(mem, -1, sizeof(mem));
  F[0] = 0;
  for (int i = 0; i < (int)((s).size()); ++i) {
    int msk = 0;
    for (int j = i; j < (int)((s).size()); ++j) {
      int d = s[j] - 'a';
      if ((1 << d) & msk) break;
      msk |= (1 << d);
      F[msk] = __builtin_popcount(msk);
    }
  }
  int ans = 0;
  for (int msk = 0; msk < (1 << H); ++msk)
    if (F[msk] != -1)
      ans = max(ans, __builtin_popcount(msk) + solve(inverse(msk)));
  cout << ans << '\n';
  return 0;
}
