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.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;

public class Main {
	
	public static Reader in = new Reader();
	public static Writer out = new Writer();
	
	public static void main(String[] args) {
		int n = in.readInt();
		int m = in.readInt();
		
		int[][] a = new int[n][m];
		
		for(int i=0; i<n; i++) {
			for(int j=0; j<m; j++) {
				a[i][j] = in.readInt();
			}
		}
		
		out.println(getAns(a, n, m));
		
		out.close();
	}
	
	public static int getAns(int[][] a, int n, int m) {
		while(isMirror(a, n, m)) {
			n /= 2;
		}
		
		return n;
	}
	
	public static boolean isMirror(int[][] a, int n, int m) {
		if((n & 1) > 0) {
			return false;
		}
		
		for(int i=0, j=n-1; i<j; i++, j--) {
			for(int k=0; k<m; k++) {
				if(a[i][k] != a[j][k]) {
					return false;
				}
			}
		}
		
		return true;
	}
	
}

class Reader {
	
	private static final int SIZE = 1<<13;
	
	private static InputStream in = System.in;
	
	private int offSet;
	private int bufferSize;
	private byte[] buffer;
	
	private char[] charBuffer;
	
	public Reader() {
		buffer = new byte[SIZE];
		charBuffer = new char[SIZE];
	}
	
	public int readInt() {
		int number = 0;
		boolean neg = false;
		
		try {
			if(offSet == bufferSize) {
				offSet = 0;
				bufferSize = in.read(buffer);
			}
			
			for(; offSet < bufferSize && buffer[offSet] != '-' && buffer[offSet] < '0'; offSet++) {
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			if(buffer[offSet] == '-') {
				neg = true;
				offSet++;
				if(offSet == bufferSize) {
					offSet = 0;
					bufferSize = in.read(buffer);
				}
			}
			
			for(; offSet < bufferSize && buffer[offSet] >= '0' && buffer[offSet] <= '9'; offSet++) {
				number = number * 10 - '0' + buffer[offSet];
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			offSet++;
		} catch(IOException io) {
			io.printStackTrace();
			System.exit(0);
		}
		
		return neg ? -number : number;
	}
	
	public long readLong() {
		long number = 0;
		boolean neg = false;
		
		try {
			if(offSet == bufferSize) {
				offSet = 0;
				bufferSize = in.read(buffer);
			}
			
			for(; offSet < bufferSize && buffer[offSet] != '-' && buffer[offSet] < '0'; offSet++) {
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			if(buffer[offSet] == '-') {
				neg = true;
				offSet++;
				if(offSet == bufferSize) {
					offSet = 0;
					bufferSize = in.read(buffer);
				}
			}
			
			for(; offSet < bufferSize && buffer[offSet] >= '0' && buffer[offSet] <= '9'; offSet++) {
				number = number * 10 - '0' + buffer[offSet];
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			offSet++;
		} catch(IOException io) {
			io.printStackTrace();
			System.exit(0);
		}
		
		return neg ? -number : number;
	}
	
	public double readDouble() {
		return Double.parseDouble(readWord());
	}
	
	public String readLine() {
		StringBuffer sb = new StringBuffer();
		
		try {
			if(offSet == bufferSize) {
				offSet = 0;
				offSet = in.read(buffer);
			}
			
			for(; offSet < bufferSize && buffer[offSet] < ' '; offSet++) {
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			if(bufferSize == -1) {
				return null;
			}
			
			int count = 0;
			
			for(; offSet < bufferSize && buffer[offSet] != '\r' && buffer[offSet] != '\n'; offSet++) {
				charBuffer[count] = (char)buffer[offSet];
				
				count++;
				
				if(count == SIZE) {
					count = 0;
					sb.append(charBuffer, 0, count);
				}
				
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			offSet++;
			
			sb.append(charBuffer, 0, count);
		} catch(IOException io) {
			io.printStackTrace();
			System.exit(0);
		}
		
		return sb.toString();
	}
	
	public String readWord() {
		StringBuffer sb = new StringBuffer();
		
		try {
			if(offSet == bufferSize) {
				offSet = 0;
				offSet = in.read(buffer);
			}
			
			for(; offSet < bufferSize && buffer[offSet] < ' '; offSet++) {
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			if(bufferSize == -1) {
				return null;
			}
			
			int count = 0;
			
			for(; offSet < bufferSize && buffer[offSet] != ' ' && buffer[offSet] != '\r' && buffer[offSet] != '\n'; offSet++) {
				charBuffer[count] = (char)buffer[offSet];
				
				count++;
				
				if(count == SIZE) {
					count = 0;
					sb.append(charBuffer, 0, count);
				}
				
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			offSet++;
			
			sb.append(charBuffer, 0, count);
		} catch(IOException io) {
			io.printStackTrace();
			System.exit(0);
		}
		
		return sb.toString();
	}

	public char[] readWord(int n) {
		char[] word = new char[n];
		
		try {
			if(offSet == bufferSize) {
				offSet = 0;
				offSet = in.read(buffer);
			}
			
			for(; offSet < bufferSize && buffer[offSet] < ' '; offSet++) {
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			if(bufferSize == -1) {
				return null;
			}
			
			for(int wi=0; offSet < bufferSize && buffer[offSet] != '\r' && buffer[offSet] != '\n'; offSet++) {
				word[wi++] = (char)buffer[offSet];
				
				if(offSet == bufferSize-1) {
					offSet = -1;
					bufferSize = in.read(buffer);
				}
			}
			
			offSet++;
		} catch(IOException io) {
			io.printStackTrace();
			System.exit(0);
		}
		
		return word;
	}

}

class Writer {
	
	private BufferedWriter output;
	
	public Writer() {
		output = new BufferedWriter(new OutputStreamWriter(System.out));
	}
	
	public void println() {
		try {
			output.append("\n");
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}

	public void print(Object o) {
		try {
			output.append(o.toString());
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void println(Object o) {
		try {
			output.append(o.toString()+"\n");
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}

	public void printf(String format, Object... args) {
		try {
			output.append(String.format(format, args));
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void printfln(String format, Object... args) {
		try {
			output.append(String.format(format, args)+"\n");
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void flush() {
		try {
			output.flush();
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void close() {
		try {
			output.close();
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}

}