code: def area(p):
      
      A = 0
      for i in range(len(p)):
          A += p[i - 1][0] * p[i][1] - p[i][0] * p[i - 1][1]
      return A / 2.
docs: Area of a polygone
  
      :param p: list of the points taken in any orientation,
                p[0] can differ from p[-1]
      :returns: area
      :complexity: linear