import java.util.*;
import java.io.*;
public class Main {
    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        char[] c = fs.next().toCharArray();
        Set<Character> set = new HashSet<>();
        for (char value : c) {
            set.add(value);
        }
        char[] tmp = new char[c.length];
        char[] tmp2 = new char[c.length];
        boolean flag;
        int min = 101;
        int i;
        char[] tmp3;
        if(set.size()==1){
            System.out.println(0);
            return;
        }
        for(char ch : set){
            for (i = 0; i < c.length; i++) {
                tmp[i] = c[i];
            }
            flag = true;
            for(i=0;i<c.length-1 && flag ;i++){
                flag = false;
                for(int j=0;j<c.length-1-i;j++){
                    if(tmp[j]==ch || tmp[j+1]==ch){
                        tmp2[j] = ch;
                    }else{
                        tmp2[j] = tmp[j];
                        flag = true;
                    }
                }
                tmp3 = tmp;
                tmp = tmp2;
                tmp2 = tmp3;
            }
            min = Math.min(i,min);
        }
        System.out.println(min);
    }

    static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;
        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            }else{
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }
        private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
        private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
        public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
        public String next() {
            if (!hasNext()) throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while(isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }
        public long nextLong() {
            if (!hasNext()) throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while(true){
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                }else if(b == -1 || !isPrintableChar(b)){
                    return minus ? -n : n;
                }else{
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }
        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
            return (int) nl;
        }
        public double nextDouble() { return Double.parseDouble(next());}
    }
}


Measured memory_bytes: 21588