new_contents: #https://codility.com/demo/results/trainingWKXGGR-SN3/
  def solution(A):
      N = len(A)
      B = N * [0]
      extras = 0
      for elem in A:
          if elem <= N and elem > 0:
              B[elem-1] = elem
      for i in xrange(N):
          if B[i] == 0:
              return i+1
      return N+1
  
subject: Create MissingInteger.py