#include <bits/stdc++.h>
#include <iomanip>
#include <math.h>
#include <unistd.h>
#include <stdio.h>
#define all(a) (a).begin(),(a).end()
#define vecin(a) rep(i,a.size())cin >> a[i]
#define vecout(a) rep(i,a.size()){cout << a[i];cout << (i == a.size() - 1 ? "\n":" ");}
#define rep(i,x) for(ll i = 0;i<x;i++)
#define REP(i,x) for(ll i = 1;i<=x;i++)
#define mp make_pair
using ll = long long;
using ld = long double;
using namespace std;
using dou = double;
const ll inf = 2147483647;
const ll INF = 1LL << 62;
const dou pi = 3.14159265358;
const ll mod = 1000000007LL;
//const ll mod = 998244353LL;
typedef pair<ll,ll> P;
using graph = vector<vector<ll>>;
template<class T, class U> inline bool chmin(T& a, const U& b){ if(a > b){ a = b; return 1; } return 0; }
template<class T, class U> inline bool chmax(T& a, const U& b){ if(a < b){ a = b; return 1; } return 0; }
template<class T, class U> inline bool change(T& a,U& b){if(a > b){swap(a,b);return 1;}return 0;}
template<class T>
T gcd(T a,T b){
    if(a < b)swap(a,b);
    if(a % b == 0)return b;
    else return gcd(b,a%b);
}
template<class T>
T lcm(T a,T b){
    return a / gcd(a,b) * b;
}

//素数判定O(sqrt(N))
template<class T>
inline bool isp(T n){
    bool res = true;
    if(n == 1)return false;
    else{
        for(ll i = 2;i * i <= n;i++){
            if(n % i == 0){
                res = false;
                break;
            }
        }
        return res;
    }
}
const ll cmax = 1000000;
vector<ll> fac(cmax),finv(cmax),inv(cmax);

// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (ll i = 2; i < cmax; i++){
        fac[i] = fac[i - 1] * i % mod;
        inv[i] = mod - inv[mod%i] * (mod / i) % mod;
        finv[i] = finv[i - 1] * inv[i] % mod;
    }
}

// 二項係数計算
ll nCk(ll n, ll k){
    if(fac[0] == 0)COMinit();
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % mod) % mod;
}
//nのm乗をMODで割ったあまりO(logm)
ll modpow(ll n,ll m,ll MOD){
    if(m == 0)return 1;
    if(m < 0)return -1;
    ll res = 1;
    while(m){
        if(m & 1)res = (res * n) % MOD;
        m >>= 1;
        n *= n;
        n %= MOD;
    }
    return res;
}
ll mypow(ll n,ll m){
    if(m == 0)return 1;
    if(m < 0)return -1;
    ll res = 1;
    while(m){
        if(m & 1)res = (res * n);
        m >>= 1;
        n *= n;
    }
    return res;
}


int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    string S;
    cin >> S;
    ll s = S.size();
    map<char,ll> ma;
    for(char c : S){
        ma[c]++;
    }
    /*for(auto x : ma){
        cout << x.first << ":" << x.second << "\n";
    }*/
    string mae,ato;
    ll ans = INF;
    ll cnt = 0;
    for(auto x : ma){
        mae = S;
        for(cnt = 0;cnt < 105;cnt++){
            ato = "";
            bool ok = 0;
            //cout << mae << "\n";
            ll t = mae.size();
            rep(i,t - 1){
                if(mae[i] != mae[i + 1]){
                    ok = 1;
                }
            }
            if(!ok)break;
            rep(i,t - 1){
                if(mae[i] == x.first || mae[i + 1] == x.first){
                    ato += x.first;
                }
                else{
                    ato += mae[i];
                }
            }
            //cout << mae << "\n";
            mae = ato;
            //cout << ato << "\n";
        }
        chmin(ans,cnt);
        //cout << "\n";
    }
    cout << ans << endl;
}


Measured memory_bytes: 26532