B'Leo Jr. draws pictures in his notebook with checkered sheets (that is, each sheet has a regular square grid printed on it). We can assume that the sheets are infinitely large in any direction. To draw a picture, Leo Jr. colors some of the cells on a sheet gray. He considers the resulting picture beautiful if the following conditions are satisfied: Leo Jr. is now struggling to draw a beautiful picture with a particular choice of n . Help him, and provide any example of a beautiful picture. To output cell coordinates in your answer, assume that the sheet is provided with a Cartesian coordinate system such that one of the cells is chosen to be the origin (0, 0) , axes 0x and 0y are orthogonal and parallel to grid lines, and a unit step along any axis in any direction takes you to a neighbouring cell. The only line contains a single integer n ( 1 <= q n <= q 500 ) -- the number of gray cells with all gray neighbours in a beautiful picture. In the first line, print a single integer k -- the number of gray cells in your picture. For technical reasons, k should not exceed 5 cdot 10^5 . Each of the following k lines should contain two integers -- coordinates of a gray cell in your picture. All listed cells should be distinct, and the picture should satisdfy all the properties listed above. All coordinates should not exceed 10^9 by absolute value. One can show that there exists an answer satisfying all requirements with a small enough k . The answer for the sample is pictured below: '...