output_description: Print Joisino's maximum possible eventual happiness.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      N M
      A_1 A_2 ... A_{N-1}
      B_{1,1} B_{1,2} ... B_{1,M}
      B_{2,1} B_{2,2} ... B_{2,M}
      :
      B_{N,1} B_{N,2} ... B_{N,M}
attempt: import sys
  
  read = sys.stdin.buffer.read
  readline = sys.stdin.buffer.readline
  readlines = sys.stdin.buffer.readlines
  from collections import defaultdict
  import time
  
  
  def main():
      s = time.time()
  
      n, m = map(int, readline().split())
      a = list(map(int, readline().split()))
      b = list(map(int, read().split()))
  
      query = [defaultdict(int) for _ in range(n + 2)]
  
      for i in range(m):
          left = list(range(-1, n + 1))
          right = list(range(1, n + 3))
  
          bi = [(val, j) for j, val in enumerate(b[i::m], 1)]
          bi.sort()
          for val, j in bi:
              l = left[j]
              r = right[j]
              query[l + 1][j] += val
              query[l + 1][r] -= val
              query[j + 1][j] -= val
              query[j + 1][r] += val
              right[l] = r
              left[r] = l
  
      imos = [0] * (n + 2)
      for i, ai in enumerate(a, 2):
          imos[i] = imos[i - 1] - ai
          query[i][i] += ai
  
      ans = 0
      for i in range(1, n + 1):
          next = [0] * (n + 2)
          for j, val in query[i].items():
              next[j] += val
  
          for j in range(i - 1, n + 1):
              next[j + 1] += next[j]
              imos[j] += next[j]
          ans = max(ans, max(imos[i : n + 1]))
  
          if time.time() - s > 1.9:
              print(ans)
              exit()
  
      print(ans)
  
  
  if __name__ == "__main__":
      main()
  
  """
  嘘解答です
  """
  
problem_description: Statement
  
  There are N barbecue restaurants along a street. The restaurants are numbered
  1 through N from west to east, and the distance between restaurant i and
  restaurant i+1 is A_i.
  
  Joisino has M tickets, numbered 1 through M. Every barbecue restaurant offers
  barbecue meals in exchange for these tickets. Restaurant i offers a meal of
  _deliciousness_ B_{i,j} in exchange for ticket j. Each ticket can only be used
  once, but any number of tickets can be used at a restaurant.
  
  Joisino wants to have M barbecue meals by starting from a restaurant of her
  choice, then repeatedly traveling to another barbecue restaurant and using
  unused tickets at the restaurant at her current location. Her eventual
  _happiness_ is calculated by the following formula: "(The total deliciousness
  of the meals eaten) - (The total distance traveled)". Find her maximum
  possible eventual happiness.
samples: [{"input": "3 4\n    1 4\n    2 2 5 1\n    1 3 3 2\n    2 2 5 1", "output": "11\n    \n\nThe eventual happiness can be maximized by the following strategy: start from\nrestaurant 1 and use tickets 1 and 3, then move to restaurant 2 and use\ntickets 2 and 4.\n\n* * *"}, {"input": "5 3\n    1 2 3 4\n    10 1 1\n    1 1 1\n    1 10 1\n    1 1 1\n    1 1 10", "output": "20"}]