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.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.BitSet;
import java.util.StringTokenizer;


public class sol {
	//...................... Global Variables .......................//
	static BitSet prime;             // used in seive generation
	// true = not prime     and false = prime
	//...................... Global Variables .......................//
	
	
	
	
	
	//===================  PROBLEM SOLVING COMES HERE ===== START  ====================//
	
    void solve() throws IOException, Exception {
    	int n = in.nextInt();
    	int m = in.nextInt();
    	
    	
    	if(n%2 ==1 || n ==1)
    	{
    		out.print(n);
    		return;
    	}
    	
    	int[][] mat = new int[n + 1][m + 1];
        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= m; ++j) {
                mat[i][j] = in.nextInt();
            }
        }
    	
    //	int result =0;
    	
    	int check=0;
    	while (n % 2 == 0) {
            for (int i = 1; i <= n / 2 && check != 1; ++i) {
                for (int j = 1; j <= m; ++j) {
                    if (mat[i][j] != mat[n - i + 1][j]) {
                        check = 1;
                        break;
                    }
                }
            }
            if (check == 1) {
                break;
            } else {
                n /= 2;
            }
    	}
    	System.out.println(n);
    			
    }
    
    //===================  PROBLEM SOLVING COMES HERE ===== END ======================//
    
    
    
    
    
    
    public static void main(String[] args) throws FileNotFoundException, IOException, Exception {
    	
    	//--------------------------------- Console I/O ------------------------------//
    	   in = new FastScanner(new BufferedReader(new InputStreamReader(System.in)));
           out = new PrintWriter(System.out);
    	//--------------------------------- Console I/O ------------------------------//
    	
    	
    	//--------------------------------- File I/O ---------------------------------//
        //   in = new FastScanner(new BufferedReader(new FileReader("input.txt")));
        //   out = new PrintWriter(new FileWriter("output.txt"));
        //--------------------------------- File I/O ---------------------------------//
        new sol().solve();
        out.close();
    }
    
    
    static FastScanner in;
    static PrintWriter out;

    static class FastScanner {
        BufferedReader in;
        StringTokenizer st;

        public FastScanner(BufferedReader in) {
            this.in = in;
        }

        public String nextToken() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(in.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public int nextInt() { return Integer.parseInt(nextToken()); }
        public long nextLong() { return Long.parseLong(nextToken()); }
        public double nextDouble() { return Double.parseDouble(nextToken()); }
        public BigInteger BigInteger()throws Exception { return new BigInteger(nextToken()); }
        public String next() throws IOException { return nextToken(); }
        public String nextLine() throws IOException { return in.readLine(); }
        
    }
}