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Competitions

# Print the chessboard

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 even sum of coordinates from left to right from top to bottom. The rest n2 - ceil(n2 / 2) numbers from ceil(n2 / 2) + 1 to n2 are written in the cells with odd sum of coordinates from left to right from top to bottom. The operation ceil(x / y) means division x by y rounded up.

#### Input

One integer n (1n9).

#### Output

Print the matrix - the chessboard in the given manner. Watch for allignment!

Time limit 1 second
Memory limit 128 MiB
Input example #1
5

Output example #1
 1 14  2 15  3
16  4 17  5 18
6 19  7 20  8
21  9 22 10 23
11 24 12 25 13

Input example #2
6

Output example #2
 1 19  2 20  3 21
22  4 23  5 24  6
7 25  8 26  9 27
28 10 29 11 30 12
13 31 14 32 15 33
34 16 35 17 36 18