#include <bits/stdc++.h>
using namespace std;
const int maxn = 101010;
string str;
bool isGood[(1 << 20) + 1];
int n, ans, arr[(1 << 20) + 1], dp[(1 << 20) + 1][22];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> str, n = (int)str.size();
  for (int i = 0; i < n; ++i) {
    int mask = 0, bit = 0;
    for (int j = i; j < n; ++j) {
      bit = str[j] - 97;
      if (mask & (1 << bit)) break;
      mask |= (1 << bit);
      isGood[mask] = true;
      dp[mask][0] = j - i + 1;
    }
  }
  for (int mask = 0; mask < (1 << 20); ++mask) {
    for (int i = 1; i <= 20; ++i) {
      if (mask & (1 << (i - 1)))
        dp[mask][i] = max(dp[mask][i - 1], dp[mask ^ (1 << (i - 1))][i - 1]);
      else
        dp[mask][i] = dp[mask][i - 1];
    }
    arr[mask] = dp[mask][20];
  }
  for (int mask = 0; mask < (1 << 20); ++mask) {
    if (isGood[mask]) ans = max(ans, arr[mask] + arr[mask ^ ((1 << 20) - 1)]);
  }
  cout << ans << endl;
  return 0;
}
