#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e6 + 100;
char s[maxn];
int a[maxn];
int b[maxn];
int flag[maxn];
int main() {
  int mx = (1 << 20) - 1;
  scanf("%s", s + 1);
  int n = strlen(s + 1);
  memset(b, -1, sizeof b);
  for (int i = 1; i <= n; i++) {
    int x = 0, c = 0;
    for (int j = i; j <= n; j++) {
      int bit = s[j] - 'a';
      if ((x >> bit) & 1) break;
      x |= (1 << bit);
      c++;
      a[x] = c;
      b[mx ^ x] = c;
    }
  }
  for (int j = 0; j <= 20; j++) {
    for (int i = 0; i < mx; i++) {
      if ((i >> j) & 1) a[i] = max(a[i], a[i ^ (1 << j)]);
    }
  }
  int ans = 0;
  for (int i = 0; i < mx; i++) {
    if (b[i] >= 0) {
      ans = max(ans, a[i] + b[i]);
    }
  }
  printf("%d\n", ans);
  return 0;
}
