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.util.*;

import java.io.*;
import java.math.BigDecimal;
import java.math.BigInteger;

import static java.lang.Math.*;
import static java.util.Arrays.*;
import static java.util.Collections.*;

import static java.lang.Integer.*;


 
 
public class Main {
	public static void main(String[] args) throws Exception{
		InputReader in = new InputReader(System.in);
		PrintWriter out = new PrintWriter(System.out);
		TaskA solver = new TaskA();
		solver.solve(1, in, out);
		out.close();
	}

static class TaskA {
  // GCD && LCM 
	 long gcd(long a ,long b){return b == 0 ? a : gcd(b , a % b);}
	 long lcm(long a , long b){return a*(b/gcd(a, b));}
 
	 // REverse a String 
	String rev(String s){
		return new StringBuilder(s).reverse().toString();
	}
	/*          SOLUTION  IS RIGHT HERE     */
	public void solve(int testNumber, InputReader in, PrintWriter out) throws IOException{
		 //BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
		//  Scanner sc = new Scanner(System.in);
      
	  int n = in.nextInt() , m = in.nextInt();
      int[][] grid = new int[n][m];
      
      for(int i = 0; i < n; i++){
    	  for(int j = 0; j < m; j++)
    		  grid[i][j] = in.nextInt();
      }
      int row = n;
      boolean bool = true;
      while(bool){
    	  if(row % 2 != 0)break;
    	  for(int i = 0; i < row/2; i++){
    		 for(int j = 0; j < m; j++){
    		  if(grid[i][j] != grid[row - i -1][j]){
    			bool = false;
    			break;
    		  }
    		 }
    	  }
    	  if(bool)row = row /2;
      }
      out.println(row);
  }
} 

 // ||||||| INPUT READER ||||||||
 static class InputReader {
	private byte[] buf = new byte[8000];
	private int index;
	private int total;
	private InputStream in;
	BufferedReader br = new  BufferedReader(new InputStreamReader(System.in));
	public InputReader(InputStream stream){
		in = stream;
	}
	
	public int scan(){
		if(total == -1)
			throw new InputMismatchException();
		if(index >= total){
			index = 0; 
			try{
			total = in.read(buf);
			}catch(IOException e){
			   throw new InputMismatchException();
			}
			if(total <= 0)
				return -1;
		}
		return buf[index++];
	}
	public long scanlong(){
		long integer = 0;
		int n = scan();
		while(isWhiteSpace(n))
			n = scan();
		int neg = 1;
		if(n == '-'){
			neg = -1;
			n = scan();
		}
		while(!isWhiteSpace(n)){
			if(n >= '0' && n <= '9'){
				integer *= 10;
				integer += n - '0';
				n = scan();
			}
			else throw new InputMismatchException();
		}
		return neg*integer;
	}
	
	private int scanInt() {
		int integer = 0;
		int n = scan();
		while(isWhiteSpace(n))
			n = scan();
		int neg = 1;
		if(n == '-'){
			neg = -1;
			n = scan();
		}
		while(!isWhiteSpace(n)){
			if(n >= '0' && n <= '9'){
				integer *= 10;
				integer += n - '0';
				n = scan();
			}
			else throw new InputMismatchException();
		}
		return neg*integer;
	}
	
	public double scandouble(){
		double doubll = 0;
		int n = scan();
		int neg = 1;
		while(isWhiteSpace(n))
			n = scan();
		if(n == '-'){
			neg = -1;
			n = scan();
		}
		while(!isWhiteSpace(n) && n != '.'){
			if(n >= '0' && n <= '9'){
				doubll *= 10;
				doubll += n - '0';
				n = scan();
			}
		}
		if(n == '.'){
			n = scan();
			double temp = 1;
			while(!isWhiteSpace(n)){
				if(n >= '0' && n <= '9'){
					temp /= 10;
					doubll += (n - '0')*temp;
					n = scan();
				}
			}
		}
		return neg*doubll;
	}
	
	private float scanfloat() {
		float doubll = 0;
		int n = scan();
		int neg = 1;
		while(isWhiteSpace(n))
			n = scan();
		if(n == '-'){
			neg = -1;
			n = scan();
		}
		while(!isWhiteSpace(n) && n != '.'){
			if(n >= '0' && n <= '9'){
				doubll *= 10;
				doubll += n - '0';
				n = scan();
			}
		}
		if(n == '.'){
			n = scan();
			double temp = 1;
			while(!isWhiteSpace(n)){
				if(n >= '0' && n <= '9'){
					temp /= 10;
					doubll += (n - '0')*temp;
					n = scan();
				}
			}
		}
		return neg*doubll;
	}
	public String scanstring(){
		StringBuilder sb = new StringBuilder();
		int n = scan();
		while(isWhiteSpace(n))
			n = scan();
		while(!isWhiteSpace(n)){
			sb.append((char)n);
			n = scan();
		}
		return sb.toString();
	}
	
	public String scan_nextLine() {
        int n = scan();
        while (isWhiteSpace(n))
            n = scan();
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(n);
            n = scan();
        } while (!isEndOfLine(n));
        return res.toString();
    }
	public boolean isWhiteSpace(int n){
		if(n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1)
			return true;
		return false;
	}
	
	private boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
/// Input module 	
	
	public int nextInt(){
	  return scanInt();
	}
	
	public long nextLong(){
		  return  scanlong();
		}
	
	public double nextDouble(){
		  return  scandouble();
		}
	
	public float nextFloat(){
		  return scanfloat();
		}

	public String next(){
		return scanstring();
	}
	
	public String nextLine() throws IOException{
		return scan_nextLine();
	}
	
	public int[] readIntArray(int size)  {
        int[] array = new int[size];
        for (int i = 0; i < size; i++) {
            array[i] = nextInt();
        }
        return array;
    }
}
 
}