Let's assume that we are given a matrix b of size x × y, let's determine the operation of mirroring matrix b. The mirroring of matrix b is a 2x × y matrix c which has the following properties:

  * the upper half of matrix c (rows with numbers from 1 to x) exactly matches b; 
  * the lower half of matrix c (rows with numbers from x + 1 to 2x) is symmetric to the upper one; the symmetry line is the line that separates two halves (the line that goes in the middle, between rows x and x + 1). 



Sereja has an n × m matrix a. He wants to find such matrix b, that it can be transformed into matrix a, if we'll perform on it several (possibly zero) mirrorings. What minimum number of rows can such matrix contain?

Input

The first line contains two integers, n and m (1 ≤ n, m ≤ 100). Each of the next n lines contains m integers — the elements of matrix a. The i-th line contains integers ai1, ai2, ..., aim (0 ≤ aij ≤ 1) — the i-th row of the matrix a.

Output

In the single line, print the answer to the problem — the minimum number of rows of matrix b.

Examples

Input

4 3
0 0 1
1 1 0
1 1 0
0 0 1


Output

2


Input

3 3
0 0 0
0 0 0
0 0 0


Output

3


Input

8 1
0
1
1
0
0
1
1
0


Output

2

Note

In the first test sample the answer is a 2 × 3 matrix b:
    
    
      
    001  
    110  
    

If we perform a mirroring operation with this matrix, we get the matrix a that is given in the input:
    
    
      
    001  
    110  
    110  
    001  
    
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.StringTokenizer;

/**
 * Created with IntelliJ IDEA.
 * User: AUtemuratov
 * Date: 07.04.14
 * Time: 15:43
 * To change this template use File | Settings | File Templates.
 */
public class Main {
    //static int a[] = new int[1111];
    static int A[][] = new int[111][111];
    //static boolean u[] = new boolean[1111];
    //static boolean U[][] = new boolean[1111][1111];

    //static ArrayList<Integer> list = new ArrayList<Integer>();
    //static Stack<Integer> stack = new Stack<Integer>();
    //static HashSet<Integer> set = new HashSet<Integer>();

    static FastReader fr = new FastReader(new BufferedReader(new InputStreamReader(System.in)));
    static PrintWriter pw = new PrintWriter(System.out);
    static int max = Integer.MIN_VALUE;
    static int min = Integer.MAX_VALUE;
    static int sum,cnt;
    static boolean ok;
    static int n,m,k,s;
    static int l,r;

    public static void main(String[] args) throws Exception {

        n = fr.nextInt();
        m = fr.nextInt();
        
        for (int i=1; i<=n; i++) {
            for (int j=1; j<=m; j++) {
                A[i][j] = fr.nextInt();
            }
        }
        
        

       int ans = rec(1,n);
       pw.println(ans);
        
       pw.close();
    }

    private static int rec(int b, int e) {

        if (e%2==1) {
            return e;
        }
        
        if (b==e) {
            return 1;
        }
        
        for (int i=b,k=e; i<=e; i++,k--) {
            for (int j=1; j<=m; j++) {
                if (A[i][j]!=A[k][j]) {
                    return e;
                }
            }
        }
        return rec (b,e/2);
        
    }
}

class FastReader {

    BufferedReader bf;
    StringTokenizer tk = null;
    String DELIM = " ";

    public FastReader(BufferedReader bf) {
        this.bf = bf;
    }

    public String nextToken() throws Exception {

        if(tk==null || !tk.hasMoreTokens()) {
            tk = new StringTokenizer(bf.readLine(),DELIM);
        }
        return tk.nextToken();
    }

    public int nextInt() throws Exception {
        return Integer.parseInt(nextToken());
    }

    public int nextLong() throws Exception {
        return Integer.parseInt(nextToken());
    }

    public int nextDouble() throws Exception {
        return Integer.parseInt(nextToken());
    }
}