#include <bits/stdc++.h>

using namespace std;

#define all(X) (X).begin(), (X).end()
#define pb push_back
#define rall(X) (X).rbegin(), (X).rend()
#define ll long long
#define ull unsigned long long
#define ld long double
#define fir first
#define sec second

int main() {
	string s; cin >> s;
	ll n = s.size();

	map<ll, vector<ll>> mp;
	for (ll i = 0; i < n; i++) {
		mp[s[i]].pb(i);
	}

	ll ans = 1e9;
	for (auto& i: mp) {
		ll len = max(i.sec[0] + 1, n - i.sec.back());
		for (ll j = 1; j < i.sec.size(); j++) {
			len = max(len, i.sec[j] - i.sec[j - 1]);
		}
		laza:
		ans = min(ans, len);
	}
	cout << ans;
	return 0;
}