// INCLUDES
#include <bits/stdc++.h>
#include <assert.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
//DEFINES
#define MAX 1000001
#define pii pair<int, int>
#define c1 __builtin_popcount
#define F first
#define S second
#define all(s) begin(s), end(s)
#define MIN3POS(a, b, c) (a) = < (b) ? ((a) = < (c) ? 1 : 3) : ((b) = < (c) ? 2 : 3)
#define MAX3POS(a, b, c) (a) >= (b) ? ((a) >= (c) ? 1 : 3) : ((b) >= (c) ? 2 : 3)
#define endl '\n'
#define int long long
#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define FOR(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define IOS                           \
    ios_base::sync_with_stdio(false); \
    cin.tie(0);                       \
    cout.tie(0);
#define error(args...)                           \
    {                                            \
        string _s = #args;                       \
        replace(_s.begin(), _s.end(), ',', ' '); \
        stringstream _ss(_s);                    \
        istream_iterator<string> _it(_ss);       \
        err(_it, args);                          \
    }
//NAMESPACES
using namespace __gnu_pbds;
using namespace std;
vector<string> vec_splitter(string s)
{
    s += ',';
    vector<string> res;
    while (!s.empty())
    {
        res.push_back(s.substr(0, s.find(',')));
        s = s.substr(s.find(',') + 1);
    }
    return res;
}
void debug_out(
    vector<string> __attribute__((unused)) args,
    __attribute__((unused)) int idx,
    __attribute__((unused)) int LINE_NUM) { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T)
{
    if (idx > 0)
        cerr << ", ";
    else
        cerr << "Line(" << LINE_NUM << ") ";
    stringstream ss;
    ss << H;
    cerr << args[idx] << " = " << ss.str();
    debug_out(args, idx + 1, LINE_NUM, T...);
}
#ifdef XOX
#define debug(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __LINE__, __VA_ARGS__)
#else
#define debug(...) 42
#endif
//HELPERS

vector<int> powers2(32, 0);
void initialize()
{
    for (int i = 1; i < powers2.size(); i++)
        powers2[i] = powers2[i - 1] * 2;
}
int32_t main()
{
    IOS
        string s;
    cin >> s;
    vector<int> v[26];
    int n = s.size();
    FOR(i, 0, 26)
    {
        v[i].push_back(0);
    }
    for (int i = 0; i < s.size(); i++)
    {
        v[(int)(s[i] - 'a')].push_back(i + 1);
    }
    FOR(i, 0, 26)
    {
        v[i].push_back(n + 1);
    }
    int ans = 1e9;

    FOR(i, 0, 26)
    {
        if (v[i].size() > 2)
        {
            int mx = 0;
            for (int j = 0; j < v[i].size() - 1; j++)
                mx = max(mx, v[i][j + 1] - v[i][j] - 1);
            debug(mx);
            ans = min(ans, mx);
        }
    }
    // FOR(i,0,26) {
    //     int mx = 0;
    //     for(int j=0;j<v[i].size()-1;i++)
    //     mx = max(mx,v[i][j+1]-v[i][j]-1);
    //     debug(mx);
    //     ans = min(ans,mx);
    // }
    cout << ans;
    return 0;
}
// Use emplace back in place of pushback
// Use tie function , for object destructuring

Measured memory_bytes: 256