Score : 100 points
We have an N×N checkerboard.
From the square at the upper left corner, a square that is i squares to the right and j squares below is denoted as (i, j). Particularly, the square at the upper left corner is denoted as (0, 0).
Each square (i, j) such that i+j is even, is colored black, and the other squares are colored white.
We will satisfy the following condition by painting some of the white squares:
Achieve the objective by painting at most 170000 squares black.
The input is given from Standard Input in the following format:
N
Print the squares to paint in the following format:
K x_1 y_1 x_2 y_2 : x_K y_K
This means that a total of K squares are painted black, the i-th of which is (x_i, y_i).
The output is considered correct only if all of the following conditions are satisfied:
2
1 1 0
4
3 0 1 2 1 2 3