You are given a chessboard of size n×n. It is filled with numbers from 1 to n2 in the following way: the first ceil(n2/2) numbers from 1 to ceil(n2/2) are written in the cells with an even sum of coordinates from left to right from top to bottom. The rest of the n2−ceil(n2/2) numbers from ceil(n2/2)+1 to n2 are written in the cells with an odd sum of coordinates from left to right from top to bottom.
The operation ceil(x/y) means division x by y rounded up.
One integer n (1≤n≤9).
Print the matrix — the chessboard in the given manner. Watch for alignment!