CF906B.Seating of Students

Students went into a class to write a test and sat in some way. The teacher thought: "Probably they sat in this order to copy works of each other. I need to rearrange them in such a way that students that were neighbors are not neighbors in a new seating."

The class can be represented as a matrix with n rows and m columns with a student in each cell. Two students are neighbors if cells in which they sit have a common side.

Let's enumerate students from 1 to n·m in order of rows. So a student who initially sits in the cell in row i and column j has a number (i - 1)·m + j. You have to find a matrix with n rows and m columns in which all numbers from 1 to n·m appear exactly once and adjacent numbers in the original matrix are not adjacent in it, or determine that there is no such matrix.

学生们进入教室参加考试，并以某种方式就座。老师心想：“他们很可能是按这种顺序就座以便互相抄袭。我需要重新安排他们的座位，使得原先相邻的学生在新座位安排中不再相邻。”

教室可表示为一个 $n$ 行 $m$ 列的矩阵，每个格子中有一名学生。若两名学生所坐的格子具有公共边，则称这两名学生为相邻。

我们按行优先顺序将学生编号为 $1$ 至 $n\cdot m$：即最初坐在第 $i$ 行第 $j$ 列格子中的学生编号为 $(i-1)\cdot m + j$。你需要构造一个 $n$ 行 $m$ 列的矩阵，其中 $1$ 至 $n\cdot m$ 的每个整数恰好出现一次，且在原矩阵中相邻的两个编号，在新矩阵中所对应的格子不能相邻；或者判定这样的矩阵不存在。

The only line contains two integers n and m (1 ≤ n, m ≤ 105; n·m ≤ 105) — the number of rows and the number of columns in the required matrix.

仅一行包含两个整数 $n$ 和 $m$（$1 ≤ n, m ≤ 10^5$；$n·m ≤ 10^5$）——分别为所求矩阵的行数和列数。

If there is no such matrix, output "NO" (without quotes).

Otherwise in the first line output "YES" (without quotes), and in the next n lines output m integers which form the required matrix.

如果不存在这样的矩阵，输出 "NO"（不带引号）。

否则，第一行输出 "YES"（不带引号），接下来的 n 行中，每行输出 m 个整数，构成所要求的矩阵。

In the first test case the matrix initially looks like this:

1 2 3 4
5 6 7 8

It's easy to see that there are no two students that are adjacent in both matrices.

In the second test case there are only two possible seatings and in both of them students with numbers 1 and 2 are neighbors.

在第一个测试用例中，矩阵初始状态如下：

1 2 3 4
5 6 7 8

很容易看出，在两个矩阵中均不存在相邻的两名学生。

在第二个测试用例中，仅有两种可能的座位安排，且在这两种安排中，编号为 1 和 2 的学生均为相邻。