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 2*x* × *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 2*x*) 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?
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 *a*<sub class="lower-index">*i*1</sub>, *a*<sub class="lower-index">*i*2</sub>, ..., *a*<sub class="lower-index">*im*</sub> (0 ≤ *a*<sub class="lower-index">*ij*</sub> ≤ 1) — the *i*-th row of the matrix *a*.
line = input()
rows, cols = line.split()
rows, cols = int(rows), int(cols)

grid = []

for i in range(rows):
    line = input()
    a = [int(z) for z in line.split()]
    grid.append(a)

if rows % 2 != 0:
    print(rows)
else:
    half = int(rows / 2)
    row_count = rows
    can_go = True
    while can_go == True and row_count > 1:
        for i in range(half):
            if grid[half - i - 1] != grid[i + half]:
                can_go = False
                break;
        if can_go == True:
            row_count = int(row_count / 2)
            half = int(half / 2)

    print(row_count)
