output_description: Print N^2 distinct points that satisfy the condition in the following format:
  
      
      
      x_1 y_1
      x_2 y_2
      :
      x_{N^2} y_{N^2}
      
  
  Here, (x_i,y_i) represents the i-th chosen point. 0 ≤ x_i,y_i < 2N must hold,
  and they must be integers. The chosen points may be printed in any order. In
  case there are multiple possible solutions, you can output any.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N D_1 D_2
attempt: N, D1, D2 = map(int, input().split())
  
  for i in range(N):
      for j in range(N):
          print(str(2 * i) + " " + str(2 * j))
  
problem_description: Statement
  
  Takahashi is doing a research on sets of points in a plane. Takahashi thinks a
  set S of points in a coordinate plane is a _good set_ when S satisfies both of
  the following conditions:
  
    * The distance between any two points in S is not \sqrt{D_1}.
    * The distance between any two points in S is not \sqrt{D_2}.
  
  Here, D_1 and D_2 are positive integer constants that Takahashi specified.
  
  Let X be a set of points (i,j) on a coordinate plane where i and j are
  integers and satisfy 0 ≤ i,j < 2N.
  
  Takahashi has proved that, for any choice of D_1 and D_2, there exists a way
  to choose N^2 points from X so that the chosen points form a good set.
  However, he does not know the specific way to choose such points to form a
  good set. Find a subset of X whose size is N^2 that forms a good set.
samples: [{"input": "2 1 2", "output": "0 0\n    0 2\n    2 0\n    2 2\n    \n\nAmong these points, the distance between 2 points is either 2 or 2\\sqrt{2},\nthus it satisfies the condition.\n\n* * *"}, {"input": "3 1 5", "output": "0 0\n    0 2\n    0 4\n    1 1\n    1 3\n    1 5\n    2 0\n    2 2\n    2 4"}]