// thanks to "http://fluffyowl.hatenablog.com/entry/2018/05/25/192753"

#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
// #define int long long
// #define double long double
#define rep(i,n) for (int i=0; i<(int)(n); ++i)
#define rep1(i,n) for (int i=1; i<(int)(n); ++i)
#define repeq(i,n) for (int i=0; i<=(int)(n); ++i)
#define rep1eq(i,n) for (int i=1; i<=(int)(n); ++i)
#define rrep(i,n) for (int i=(int)(n)-1; i>=0; --i)
#define rrep1(i,n) for (int i=(int)(n)-1; i>0; --i)
#define rrepeq(i,n) for (int i=(int)(n); i>=0; --i)
#define rrep1eq(i,n) for (int i=(int)(n); i>0; --i)
#define REP(i,a,b) for (int i=(int)(a); i<=(int)(b); ++i)
#define RREP(i,a,b) for (int i=(int)(a); i>=(int)(b); --i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
template<typename T> using Graph = vector<vector<T>>;
template<typename T> using Spacial = vector<vector<vector<T>>>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int MOD = 1e9+7;
const int MOD2 = 998244353;
// const double EPS = 1e-9;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
string interval[2] = {" ", "\n"}; // {" ", "\n"}

template<typename T> struct is_plural : false_type{};
template<typename T1, typename T2> struct is_plural<pair<T1, T2>> : true_type{};
template<typename T> struct is_plural<vector<T>> : true_type{};
template<typename T> struct is_plural<complex<T>> : true_type{};
 
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << " " << p.second; }
template<typename T> istream &operator>>(istream &is, vector<T> &vec) { for (auto itr = vec.begin(); itr != vec.end(); ++itr) is >> *itr; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec) { if (vec.empty()) return os; bool pl = is_plural<T>(); os << vec.front(); for (auto itr = ++vec.begin(); itr != vec.end(); ++itr) os << interval[pl] << *itr; return os; }
 
bool CoutYN(bool a, string y = "Yes", string n = "No") { cout << (a ? y : n) << "\n"; return a; }

template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

long long modpow(int a, long long n, int mod = MOD) { long long ret = 1; do { if (n & 1) ret = ret * a % mod; a = 1LL * a * a % mod; } while (n >>= 1); return ret; }

template<typename T> T GCD(T a, T b) { return b ? GCD(b, a%b) : a; }
template<typename T> T LCM(T a, T b) { return a / GCD(a, b) * b; }

template<typename T1, typename T2> bool CompareBySecond(pair<T1, T2> a, pair<T1, T2> b) { return a.second != b.second ? a.second < b.second : a.first < b.first; }
template<typename T1, typename T2> bool CompareByInverse(pair<T1, T2> a, pair<T1, T2> b) { return a.first != b.first ? a.first < b.first : a.second > b.second; }


/* -------- <templates end> -------- */


template<class Compare>
struct RangeMinimumQuery {
  static constexpr int BLOCKSIZE = 16;
  const int sz;
  Compare comp;
  vector<int> table;
  vector<vector<int>> block;

  explicit RangeMinimumQuery(const int &n, const Compare &x) : sz(n), comp(x), block(1) {
    deque<int> dq;
    table.reserve(sz);
    block[0].reserve(sz / BLOCKSIZE);
    for (int i = 0; i < sz; ++i) {
      while (!dq.empty() && !comp(dq.back(), i)) {
        dq.pop_back();
      }
      table.emplace_back(dq.empty() ? 0 : table[dq.back()]);
      table.back() |= 1 << (i % BLOCKSIZE);
      dq.emplace_back(i);
      if (!((i + 1) % BLOCKSIZE)) {
        block[0].emplace_back(dq.front());
        dq.clear();
      }
    }
    for (int i = 1; i << 1 <= sz / BLOCKSIZE; i <<= 1) {
      vector<int> vec;
      const int cnt = sz / BLOCKSIZE + 1 - (i << 1);
      vec.reserve(cnt);
      for (int k = 0; k < cnt; ++k) {
        vec.emplace_back(get_min(block.back()[k], block.back()[k + i]));
      }
      block.emplace_back(move(vec));
    }
  }

  int get_min(const int L, const int R) const {
    return comp(L, R) ? L : R;
  }

  inline int ctz(const int n) {
    return __builtin_ctz(n);
  }

// [a, b] 0-indexed
  int query(int first, int last) {
    if (first > last) return -1;
    if (first < 0) first = 0;
    if (last >= sz) last = sz-1;
    const int L = first / BLOCKSIZE + 1;
    const int R = last / BLOCKSIZE;
    if (L < R) {
      const int d = 31 - __builtin_clz(R - L);
      int a = get_min((L - 1) * BLOCKSIZE + ctz(table[L * BLOCKSIZE - 1] & (-1 << (first % BLOCKSIZE))), block[d][L]);
      int b = get_min(block[d][R - (1 << d)], R * BLOCKSIZE + ctz(table[last]));
      return get_min(a, b);
    } else if (L == R) {
      return get_min((L - 1) * BLOCKSIZE + ctz(table[L * BLOCKSIZE - 1] & (-1 << (first % BLOCKSIZE))), R * BLOCKSIZE + ctz(table[last]));
    } else {
      return R * BLOCKSIZE + ctz(table[last] & (-1 << (first % BLOCKSIZE)));
    }
  }
};

template<class Compare>
RangeMinimumQuery<Compare> make_rmq(const int n, const Compare &x) {
  return RangeMinimumQuery<Compare>(n, x);
}

void solve() {
  int n, m; cin >> n >> m;
  vi dist(n-1); cin >> dist;
  Graph<int> taste(n, vi(m)); cin >> taste;

  Graph<ll> imos(n+1, vl(n+1, 0));
  auto f = [&](int a, int b, int idx, const int &val) -> void {
    imos[a][idx] += val;
    imos[a][b+1] -= val;
    imos[idx+1][idx] -= val;
    imos[idx+1][b+1] += val;
  };

  rep(i,m) {
    auto rmq = make_rmq(n, [&](int a, int b) { return taste[a][i] > taste[b][i]; });
    function<void(int, int)> dfs = [&](int a, int b) {
      if (a == b) {
        f(a, a, a, taste[a][i]);
        return;
      }
      int idx = rmq.query(a, b);
      f(a, b, idx, taste[idx][i]);
      if (idx != a) dfs(a, idx-1);
      if (idx != b) dfs(idx+1, b);
    };
    dfs(0, n-1);
  }

  rep1(x,n) rep(y,n) imos[x][y] += imos[x-1][y];
  rep1(y,n) rep(x,n) imos[x][y] += imos[x][y-1];

  vl sum(n, 0);
  rep1(i,n) sum[i] = sum[i-1] + dist[i-1];

  ll ans = 0;
  rep(j,n) repeq(i,j) chmax(ans, imos[i][j] - (sum[j] - sum[i]));
  cout << ans << endl;
}


/* -------- <programs end> -------- */


signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  solve();
  return 0;
}


Measured memory_bytes: 199936