#include <bits/stdc++.h>
using namespace std;
inline char gc() {
  static const long long L = 233333;
  static char sxd[L], *sss = sxd, *ttt = sxd;
  if (sss == ttt) {
    ttt = (sss = sxd) + fread(sxd, 1, L, stdin);
    if (sss == ttt) {
      return EOF;
    }
  }
  return *sss++;
}
inline char readalpha() {
  char c = gc();
  for (; !isalpha(c); c = gc())
    ;
  return c;
}
inline char readchar() {
  char c = gc();
  for (; c == ' '; c = gc())
    ;
  return c;
}
template <class T>
inline bool read(T& x) {
  bool flg = false;
  char c = gc();
  x = 0;
  for (; !isdigit(c); c = gc()) {
    if (c == '-') {
      flg = true;
    } else if (c == EOF) {
      return false;
    }
  }
  for (; isdigit(c); c = gc()) {
    x = (x << 1) + (x << 3) + (c ^ 48);
  }
  if (flg) {
    x = -x;
  }
  return true;
}
template <class T>
inline void write(T x) {
  if (x < 0) {
    putchar('-');
    x = -x;
  }
  if (x < 10) {
    putchar(x | 48);
    return;
  }
  write(x / 10);
  putchar((x % 10) | 48);
}
const int maxn = 20;
const int maxl = 1000005;
int n;
int f[1 << maxn];
int g[1 << maxn];
char s[maxl];
int main() {
  scanf("%s", s + 1);
  n = strlen(s + 1);
  for (int i = 1; i <= n; ++i) {
    int now = i, nowzt = 0;
    while (now) {
      if (nowzt & (1 << (s[now] - 'a'))) {
        break;
      }
      nowzt |= (1 << (s[now] - 'a'));
      now--;
      f[nowzt] = i - now;
    }
  }
  int ans = 0;
  for (int i = 0; i < 1 << 20; ++i) {
    g[i] = f[i];
  }
  for (int i = 0; i < 1 << 20; ++i) {
    for (int j = 0; j < 20; ++j) {
      g[i | (1 << j)] = max(g[i], g[i | (1 << j)]);
    }
  }
  for (int i = 0; i < 1 << 20; ++i) {
    ans = max(ans, f[i] + g[((1 << 20) - 1) ^ i]);
  }
  printf("%d\n", ans);
  return 0;
}
