def campo():
    
  n = 20
    
  xmin = -5
  xmax = +5
  ymin = -5
  ymax = +5
    
  dx = (xmax - xmin)/n
  dy = (ymax - ymin)/n
    
  y = ymin
  while (y < ymax):
      
    x = xmin
    while (x < xmax):

        X = -y / (x**2 + y**2)
        Y = +x / (x**2 + y**2)

        x += dx

    y += dy