A9157 | Black-and-White Cube

You are given a cube of size $k×k×k$ , which consists of unit cubes. Two unit cubes are considered neighbouring, if they have common face.

Your task is to paint each of $k^{3}$ unit cubes one of two colours (black or white), so that the following conditions must be satisfied:

- each white cube has exactly 2 neighbouring cubes of white color;
- each black cube has exactly 2 neighbouring cubes of black color.

The first line contains integer $k$ $(1<=k<=100)$ , which is size of the cube.

Print -1 if there is no solution. Otherwise, print the required painting of the cube consequently by layers. Print a $k×k$ matrix in the first $k$ lines, showing how the first layer of the cube should be painted. In the following $k$ lines print a $k×k$ matrix — the way the second layer should be painted. And so on to the last $k$ -th layer. Note that orientation of the cube in the space does not matter.

Mark a white unit cube with symbol "w" and a black one with "b". Use the format of output data, given in the test samples. You may print extra empty lines, they will be ignored.