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.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.StringTokenizer;




public class solver {
    BufferedReader in;
    PrintWriter out;
    StringTokenizer tok;
    
    String readString() throws IOException{
        while (tok==null || !tok.hasMoreTokens()){
            try{
                tok=new StringTokenizer(in.readLine());             
            }
            catch(Exception e){
                return null;
            }            
        }
        return tok.nextToken();
    }
    int readInt() throws NumberFormatException, IOException{
        return Integer.parseInt(readString());
    }
    long readLong() throws NumberFormatException, IOException{
        return Long.parseLong(readString());
    }
    double readDouble() throws NumberFormatException, IOException{
        return Double.parseDouble(readString());
    }
    
    final static boolean OJ=System.getProperty("ONLINE_JUDGE")!=null;
    
    
    void init() throws FileNotFoundException{        
        if (OJ){
            in=new BufferedReader(new InputStreamReader(System.in));
            out=new PrintWriter(System.out);  
        }else{          
            in=new BufferedReader(new FileReader("input.txt"));  
            out=new PrintWriter("output.txt");  
            
            in=new BufferedReader(new InputStreamReader(System.in));
            out=new PrintWriter(System.out);
        }
    }    
    int[] iMas(int n) throws NumberFormatException, IOException{
        int[] a=new int[n];
        for (int i=0;i<n;i++){
            a[i]=readInt();
        }
        return a;
    }
    
    
    int gcd (int a, int b) {
        if (b == 0)
            return a;
        else
            return gcd (b, a % b);
    }   
    
    
    
    class Pair implements Comparable<Pair>{
        int b;
        int d;
        String s;
        
        Pair(int x,int y,String s){
            b=x;
            d=y;            
            this.s=s;
        }
                
        @Override
        public int compareTo(Pair o) {          
            return b-o.b;
        }                       
    }
    
    
    boolean check(int[][] x,int n,int m){       
        if (n%2==1) return false;
        for (int i=0;i<m;i++){
            for (int j=0;j<n/2;j++){
                if (x[j][i]!=x[n-1-j][i]) return false;                 
            }
        }
        return true;
    }
    
    
    
    void solve() throws IOException{
        int n=readInt();
        int m=readInt();
        if (n%2==1) {
            out.println(n);
            return;
        }
        
        int[][] x=new int[n][m];
        for (int i=0;i<n;i++)x[i]=iMas(m);
        
        while (n>1){
            if (check(x,n,m)) n/=2;else break;
        }
        out.println(n);
                
        
        
    }
    
    
    void run() throws NumberFormatException, IOException{
        init();
         long h=System.currentTimeMillis();        
        solve();
         System.err.println(System.currentTimeMillis()-h);
        out.close();
    }
    
    
    

    
    public static void main(String[] args) throws NumberFormatException, IOException {
        new solver().run();
    }

}