import java.util.*;
import java.io.*;
import java.math.*;
 
public class Main {
    public static void main(String[] args) throws IOException {
        PrintWriter out = new PrintWriter(System.out);
        //Scanner sc = new Scanner();
        Reader in = new Reader();
        Main solver = new Main();
        solver.solve(out, in);
        out.flush();
        out.close();
 
    }
 
    //<>
    
    static int maxn = (int)1e5*2;
    static long mod=(int)1e9+7;
    static int n,t,m,k;
    
    static int[] add;
    static LinkedList<Node> list;
    
    void solve(PrintWriter out, Reader in) throws IOException{   
        String str  = in.next();
        add = new int[1000001];
        list = new LinkedList<>();
        
        char prev = str.charAt(0);
        int cnt = 1;
        for(int i=1;i<str.length();i++){
            if(prev!=str.charAt(i)){
                list.add(new Node(prev,cnt));
                cnt=1;
                prev = str.charAt(i);
            }else cnt++;
        }
        
        
        list.add(new Node(prev,cnt));
        
        int i=0,ans=0,size = list.size();
        Node e ;
        prev = '.';
        
        
        while(size>1){
            i=0;
            cnt=-1;
            prev='.';
            
            Iterator<Node> itr = list.iterator();
            while(itr.hasNext()){
                e = itr.next();
                if(add[i]>0) {
                    e.y+=add[i];
                    add[i]=0;
                }
                
                if(i!=0 && i!=size-1){
                    e.y -= 2;
                }else{
                    e.y--;
                }
                
                i++;
                
                if(e.y<=0) {
                    itr.remove();
                    continue;
                }else{
                    if(prev==e.c){
                        add[cnt]+=e.y;
                        itr.remove();
                        continue;
                    }else{
                        prev = e.c;
                        cnt++;
                    }
                }
                
            }

            ans++;
            size = list.size();
        }
        out.println(ans);
    }

    static class Node {
        int y;
        char c;
        
        Node(char c,int y){
            this.c = c;
            this.y = y;
        }
    }
    
    static class Edge implements Comparable<Edge> {
        int u,v,w;
        
        Edge(int u,int v,int w){
            this.u = u;
            this.v = v;
            this.w = w;
        }
        
        
        public int compareTo(Edge o){
            return this.w - o.w;
        }
    }
    
    
    static class Reader {
 
        private InputStream mIs;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
 
        public Reader() {
            this(System.in);
        }
 
        public Reader(InputStream is) {
            mIs = is;
        }
 
        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
 
        }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = mIs.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }
 
        public String nextLine() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        }
 
        public String next() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }
 
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
 
        public long nextLong() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
 
        public int nextInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
 
        public boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
 
        public boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }
 
    }
}