output_description: Find the minimum number of moves required to achieve the objective.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N M
      X_1 X_2 ... X_M
attempt: N, M = map(int, input().split())
  X_lines = str(input())
  X_lines = X_lines.split()
  X = []
  for i in range(len(X_lines)):
      X.append(int(X_lines[i]))
  
  X_arrays = X
  X_arrays.sort()
  X_max = X_arrays[len(X_arrays) - 1]
  X_min = X_arrays[0]
  X_kyokai = [X_min]
  if not N == 1:
      for i in range(N - 1):
          X_kyokai.append((i + 1 / N) * (X_max + X_min))
  X_kyokai.append(X_max)
  
  X_all_lines = [[]]
  if not len(X_kyokai) - 2 == 0:
      for i in range(len(X_kyokai) - 2):
          X_all_lines.append([])
  for i in range(len(X_kyokai) - 1):
      for j in range(M):
          if X_kyokai[i] <= X_arrays[j] and X_arrays[j] < X_kyokai[i + 1]:
              X_all_lines[i].append(X_arrays[j])
  X_all_lines[len(X_kyokai) - 2].append(X_max)
  
  sum_dif = 0
  for i in range(len(X_all_lines)):
      i_max = X_all_lines[i][len(X_all_lines[i]) - 1]
      i_min = X_all_lines[i][0]
      dif = i_max - i_min
      sum_dif = sum_dif + dif
  
  print(sum_dif)
  
problem_description: Statement
  
  We will play a one-player game using a number line and N pieces.
  
  First, we place each of these pieces at some integer coordinate.
  
  Here, multiple pieces can be placed at the same coordinate.
  
  Our objective is to visit all of the M coordinates X_1, X_2, ..., X_M with
  these pieces, by repeating the following move:
  
  **Move** : Choose a piece and let x be its coordinate. Put that piece at
  coordinate x+1 or x-1.
  
  Note that the coordinates where we initially place the pieces are already
  regarded as visited.
  
  Find the minimum number of moves required to achieve the objective.
samples: [{"input": "2 5\n    10 12 1 2 14", "output": "5\n    \n\nThe objective can be achieved in five moves as follows, and this is the\nminimum number of moves required.\n\n  * Initially, put the two pieces at coordinates 1 and 10.\n  * Move the piece at coordinate 1 to 2.\n  * Move the piece at coordinate 10 to 11.\n  * Move the piece at coordinate 11 to 12.\n  * Move the piece at coordinate 12 to 13.\n  * Move the piece at coordinate 13 to 14.\n\n* * *"}, {"input": "3 7\n    -10 -3 0 9 -100 2 17", "output": "19\n    \n\n* * *"}, {"input": "100 1\n    -100000", "output": "0"}]