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

public class MainClass
{
    static ArrayList<Integer> B = new ArrayList<>();
    static ArrayList<Character> D = new ArrayList<>();
    public static void main(String[] args)throws IOException
    {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String s = in.readLine();
        ArrayList<Integer> A = new ArrayList<>();
        ArrayList<Character> C = new ArrayList<>();
        int n = s.length();
        for (int i=0;i<n;i++)
        {
            int j = i;
            while (j < n && s.charAt(i) == s.charAt(j))
                j++;
            A.add(j - i);
            C.add(s.charAt(i));
            i = j - 1;
        }
        int count = 0;
        while (A.size() > 1)
        {
            count++;
            int minTime = Integer.MAX_VALUE;
            int m = A.size();
            for (int i=0;i<m;i++)
            {
                int x = A.get(i);
                if (i == 0)
                {
                    int time = (int)Math.ceil((double)x / 1) - 1;
                    time ++;
                    minTime = Math.min(minTime, time);
                    continue;
                }
                int time = (int)Math.ceil((double)x / 2) - 1;
                time ++;
                minTime = Math.min(minTime, time);
            }
            B.clear();
            D.clear();
            for (int i=0;i<m;i++)
            {
                int left = A.get(i);
                if (i == 0 || i == m - 1)
                    left -= minTime;
                else
                    left -= minTime * 2;
                if (left <= 0)
                    continue;
                else
                {
                    if (B.size() > 0 && D.get(D.size() - 1) == C.get(i))
                    {
                        int x = B.remove(B.size() - 1);
                        char ch = D.remove(D.size() - 1);
                        B.add(x + left);
                        D.add(ch);
                    }
                    else
                    {
                        B.add(left);
                        D.add(C.get(i));
                    }
                }
            }
            A = (ArrayList<Integer>)B.clone();
            C = (ArrayList<Character>)D.clone();
        }
        System.out.println(count);
    }
}
class Reader
{
    final private int BUFFER_SIZE = 1 << 16;
    private DataInputStream din;
    private byte[] buffer;
    private int bufferPointer, bytesRead;

    public Reader()
    {
        din = new DataInputStream(System.in);
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }

    public Reader(String file_name) throws IOException
    {
        din = new DataInputStream(new FileInputStream(file_name));
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }

    public String readLine() throws IOException
    {
        byte[] buf = new byte[64]; // line length
        int cnt = 0, c;
        while ((c = read()) != -1)
        {
            if (c == '\n')
                break;
            buf[cnt++] = (byte) c;
        }
        return new String(buf, 0, cnt);
    }

    public int nextInt() throws IOException
    {
        int ret = 0;
        byte c = read();
        while (c <= ' ')
            c = read();
        boolean neg = (c == '-');
        if (neg)
            c = read();
        do
        {
            ret = ret * 10 + c - '0';
        }  while ((c = read()) >= '0' && c <= '9');

        if (neg)
            return -ret;
        return ret;
    }

    public long nextLong() throws IOException
    {
        long ret = 0;
        byte c = read();
        while (c <= ' ')
            c = read();
        boolean neg = (c == '-');
        if (neg)
            c = read();
        do {
            ret = ret * 10 + c - '0';
        }
        while ((c = read()) >= '0' && c <= '9');
        if (neg)
            return -ret;
        return ret;
    }

    public double nextDouble() throws IOException
    {
        double ret = 0, div = 1;
        byte c = read();
        while (c <= ' ')
            c = read();
        boolean neg = (c == '-');
        if (neg)
            c = read();

        do {
            ret = ret * 10 + c - '0';
        }
        while ((c = read()) >= '0' && c <= '9');

        if (c == '.')
        {
            while ((c = read()) >= '0' && c <= '9')
            {
                ret += (c - '0') / (div *= 10);
            }
        }

        if (neg)
            return -ret;
        return ret;
    }

    private void fillBuffer() throws IOException
    {
        bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
        if (bytesRead == -1)
            buffer[0] = -1;
    }

    private byte read() throws IOException
    {
        if (bufferPointer == bytesRead)
            fillBuffer();
        return buffer[bufferPointer++];
    }

    public void close() throws IOException
    {
        if (din == null)
            return;
        din.close();
    }
}







