output_description: Print the minimum distance that needs to be traveled when you start at one of
  the houses and visit all the N houses.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      K N
      A_1 A_2 ... A_N
attempt: K, N = map(int, input().strip().split())
  A = list(map(int, input().strip().split()))
  val = [0, 0]
  for i in range(N - 1):
      distance = A[i + 1] - A[i]
      if distance > val[1]:
          val[0] = i
          val[1] = distance
  last = [N, A[0] + (K - A[N - 1])]
  if A[0] + (K - A[N - 1]) > val[1]:
      val = last
  print(K - val[1])
  
problem_description: Statement
  
  There is a circular pond with a perimeter of K meters, and N houses around
  them.
  
  The i-th house is built at a distance of A_i meters from the northmost point
  of the pond, measured clockwise around the pond.
  
  When traveling between these houses, you can only go around the pond.
  
  Find the minimum distance that needs to be traveled when you start at one of
  the houses and visit all the N houses.
samples: [{"input": "20 3\n    5 10 15", "output": "10\n    \n\nIf you start at the 1-st house and go to the 2-nd and 3-rd houses in this\norder, the total distance traveled will be 10.\n\n* * *"}, {"input": "20 3\n    0 5 15", "output": "10\n    \n\nIf you start at the 2-nd house and go to the 1-st and 3-rd houses in this\norder, the total distance traveled will be 10."}]