import java.util.Scanner;
import java.util.LinkedList;
import java.util.ListIterator;
/**
 * http://codeforces.com/problemset/problem/909/D
 * @author Alan Yan
 *	Time Limit Exceeded Test Case 15
 */
public class Task909D {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		LinkedList<Group> list = new LinkedList<Group>();
		char curr = s.charAt(0);
		Group currG = new Group(curr);
		for(int i = 1; i < s.length(); i++) {
			if(curr == s.charAt(i))
				currG.increase();
			else {
				list.add(currG);
				curr = s.charAt(i);
				currG = new Group(curr);
			}
		}
		list.add(currG);

		int ans = 0;
		while(list.size() > 1) {
			int x = Integer.MAX_VALUE;
			for(int i = 0; i < list.size(); i++) {
				x = Math.min(x, (int) Math.ceil((list.get(i).num + 0.0)/(1 + bool(i != 0 && i != list.size() - 1))));
			}
			ans += x;
			ListIterator<Group> one = list.listIterator();

			Group temp = one.next();
			temp.num -= x;
			while(one.hasNext()) {
				temp = one.next();
				temp.num -= 2*x;
			}
			temp.num += x;
			ListIterator<Group> it = list.listIterator();
			while(it.hasNext()) {
				if(it.next().num <= 0)
					it.remove();
			}
			if(list.size() > 1) {
				Group c = it.previous();
				while(!it.hasPrevious()) {
					if(c.color == it.previous().color) {
						it.next().num += c.num;
					}
					it.next(); it.remove();
					c = it.next();
				}
			}
		}
		System.out.print(ans);
		sc.close();
	}
	static int bool(boolean x) {
		if(x) return 1; return 0;
	}
	static class Group{
		char color;
		int num;
		Group(char color){
			this.color = color; num = 1;
		}
		void increase() {
			num++;
		}
	};
}