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?
输入描述:
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.
输出描述:
In the single line, print the answer to the problem — the minimum number of rows of matrix b.
示例1
输入
4 3<br />0 0 1<br />1 1 0<br />1 1 0<br />0 0 1<br />3 3<br />0 0 0<br />0 0 0<br />0 0 0<br />8 1<br />0<br />1<br />1<br />0<br />0<br />1<br />1<br />0<br />
备注:
In the first test sample the answer is a 2 × 3 matrix b:001110If we perform a mirroring operation with this matrix, we get the matrix a that is given in the input:001110110001
加载中...