import java.util.ArrayList;
import java.util.List;

public class Main {

	private static void solve() {
		char[] s = ns();
		int n = s.length;
		
		List<int[]> list = new ArrayList<>();
		char now = s[0];
		int count = 0;
		for (int i = 0; i < n; i ++) {
			if (s[i] != now) {
				list.add(new int[] {s[i - 1], count});
				now = s[i];
				count = 1;
			} else {
				count ++;
			}
		}
		if (count > 0) {
			list.add(new int[] {s[n - 1], count});
		}
		int[][] array = list.stream().toArray(size -> new int[size][]);
		
		int ret = 0;
		n = array.length;
		while (n > 1) {
			ret ++;
			for (int i = 0; i < n; i ++) {
				if (i == 0 || i == n - 1) {
					array[i][1] --;
				} else {
					array[i][1] -= 2;
				}
			}
			int ptr = 0;
			
			for (int i = 0; i < n;) {
				if (array[i][1] > 0) {
					int v = 0;
					int q = i;
					while (q < n && (array[q][1] <= 0 || array[q][0] == array[i][0])) {
						v += array[q][1] <= 0 ? 0 : array[q][1];
						q ++;
					}
					array[ptr][1] = v;
					array[ptr][0] = array[i][0];
					ptr ++;
					i = q;
				} else {
					i ++;
				}
			}
			n = ptr;
		}
		System.out.println(ret);
	}

	public static void main(String[] args) {
		new Thread(null, new Runnable() {
			@Override
			public void run() {
				long start = System.currentTimeMillis();
				String debug = args.length > 0 ? args[0] : null;
				if (debug != null) {
					try {
						is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
					} catch (Exception e) {
						throw new RuntimeException(e);
					}
				}
				reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
				solve();
				out.flush();
				tr((System.currentTimeMillis() - start) + "ms");
			}
		}, "", 64000000).start();
	}

	private static java.io.InputStream is = System.in;
	private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
	private static java.util.StringTokenizer tokenizer = null;
	private static java.io.BufferedReader reader;

	public static String next() {
		while (tokenizer == null || !tokenizer.hasMoreTokens()) {
			try {
				tokenizer = new java.util.StringTokenizer(reader.readLine());
			} catch (Exception e) {
				throw new RuntimeException(e);
			}
		}
		return tokenizer.nextToken();
	}

	private static double nd() {
		return Double.parseDouble(next());
	}

	private static long nl() {
		return Long.parseLong(next());
	}

	private static int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private static char[] ns() {
		return next().toCharArray();
	}

	private static long[] nal(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	}

	private static int[][] ntable(int n, int m) {
		int[][] table = new int[n][m];
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				table[i][j] = ni();
			}
		}
		return table;
	}

	private static int[][] nlist(int n, int m) {
		int[][] table = new int[m][n];
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				table[j][i] = ni();
			}
		}
		return table;
	}

	private static int ni() {
		return Integer.parseInt(next());
	}

	private static void tr(Object... o) {
		if (is != System.in)
			System.out.println(java.util.Arrays.deepToString(o));
	}
}
