import java.io.*;
import java.util.*;

class Main {
    static int res = Integer.MAX_VALUE;
    
    public static void main(String args[]) throws IOException {
        Scan sc = new Scan();
        char[] carr = sc.scanString().toCharArray();
        int len = carr.length;
        if(len == 1){
            System.out.println(0);
            return;
        }
        if(len == 2){
            System.out.println(carr[0] == carr[1] ? 0 : 1);
            return;
        }
        
        for(Character c : carr){
            recur(carr, 0, c);
        }
        
        System.out.println(res);
    }
    
    static void recur(char[] src, int soFar, char best){
        char[] nxt = new char[src.length-1];
        int cnt = 0;
        for(int i = 0, end = nxt.length; i < end; ++i){
            char curr = src[i];
            char foll = src[i+1];
            if(curr == best || foll == best){
                nxt[i] = best;
                if(curr == foll)
                    ++cnt;
                continue;
            }
            else 
                nxt[i] = curr;
        }
        if(cnt==nxt.length){
            res = Math.min(res,soFar);
            return;
        }
        recur(nxt, soFar+1, best);
    }
}

class Scan
{
    private byte[] buf=new byte[1024];
    private int index;
    private InputStream in;
    private int total;
    public Scan()
    {
        in=System.in;
    }
    public int scan()throws IOException
    {
        if(total<0)
        throw new InputMismatchException();
        if(index>=total)
        {
            index=0;
            total=in.read(buf);
            if(total<=0)
            return -1;
        }
        return buf[index++];
    }
    public int scanInt()throws IOException
    {
        int integer=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n))
        {
            if(n>='0'&&n<='9')
            {
                integer*=10;
                integer+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        return neg*integer;
    }
    public long scanLong() throws IOException {
        long integer=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n))
        {
            if(n>='0'&&n<='9')
            {
                integer*=10;
                integer+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        return neg*integer;
    }
    public double scanDouble()throws IOException
    {
        double doub=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n)&&n!='.')
        {
            if(n>='0'&&n<='9')
            {
                doub*=10;
                doub+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        if(n=='.')
        {
            n=scan();
            double temp=1;
            while(!isWhiteSpace(n))
            {
                if(n>='0'&&n<='9')
                {
                    temp/=10;
                    doub+=(n-'0')*temp;
                    n=scan();
                }
                else throw new InputMismatchException();
            }
        }
        return doub*neg;
    }
    public String scanString()throws IOException
    {
        StringBuilder sb=new StringBuilder();
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        while(!isWhiteSpace(n))
        {
            sb.append((char)n);
            n=scan();
        }
        return sb.toString();
    }
    private boolean isWhiteSpace(int n)
    {
        if(n==' '||n=='\n'||n=='\r'||n=='\t'||n==-1)
        return true;
        return false;
    }
}


Measured memory_bytes: 21964