#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int t;
  string s;
  cin >> s;
  long long int n = s.length();
  long long int dp[s.length() + 5][27];
  for (int i = 0; i <= s.length(); i++) {
    for (int j = 0; j < 27; j++) dp[i][j] = 0;
  }
  for (int i = 0; i < s.length(); i++) {
    if (i != 0) {
      for (int j = 0; j < 27; j++) {
        dp[i + 1][j] = dp[i][j];
      }
    }
    dp[i + 1][s[i] - 'a']++;
  }
  long long int ans = 1000000000000000000;
  for (char c = 'a'; c <= 'z'; c++) {
    long long int low = 1, high = n;
    long long int mid;
    while (low <= high) {
      mid = (low + high) / 2;
      bool f = 1;
      for (int i = mid; i <= n; i++) {
        if (dp[i][c - 'a'] - dp[i - mid][c - 'a'] <= 0) {
          f = 0;
        }
      }
      if (f) {
        high = mid - 1;
      } else {
        low = mid + 1;
      }
    }
    ans = min(low, ans);
  }
  cout << ans << endl;
}
