#include <bits/stdc++.h>
using namespace std;
char s[101010];
int l[30], r[30], ans = 0x3f3f3f3f;
int main() {
  scanf("%s", s + 1);
  int len = strlen(s + 1);
  for (int i = 1; i <= len; i++) {
    int now = s[i] - 'a';
    l[now] = max(l[now], i - r[now]);
    r[now] = i;
  }
  for (int i = 0; i < 26; i++) {
    if (l[i] != 0) {
      l[i] = max(l[i], len - r[i] + 1);
    }
  }
  for (int i = 0; i < 26; i++) {
    if (l[i] != 0) {
      ans = min(ans, l[i]);
    }
  }
  printf("%d\n", ans);
  return 0;
}
