#ifndef __SEGMENT_TREE_H__
#define __SEGMENT_TREE_H__

/* updated: 2019-10-05 */

#include <vector>
#include <functional>
#include <algorithm>
#include <limits>
#include <cassert>
#include <iostream>
#include <string>
#include <sstream>

/*-- てんぷれ --*/
struct HogeMonoid {
	using Type = int;
	static Type identity() {
		return Type();
	}
	static Type operate(const Type& left, const Type& right) {
		return Type();
	}
};

/*--------------*/

namespace Monoid {
	template <class T>
	struct Sum {
		using Type = T;
		static Type identity() {
			return T();
		}
		static Type operate(const Type& left, const Type& right) {
			return left + right;
		}
	};

	template <class T>
	struct Minimum {
		using Type = T;
		static Type identity() {
			return std::numeric_limits<Type>::max();
		}
		static Type operate(const Type& left, const Type& right) {
			return std::min(left, right);
		}
	};

	template <class T>
	struct Maximum {
		using Type = T;
		static Type identity() {
			return std::numeric_limits<Type>::min();
		}
		static Type operate(const Type& left, const Type& right) {
			return std::max(left, right);
		}
	};
}

/* 注意: コンストラクタの引数は size でない */
template <class Monoid>
class SegmentTree {
	using T = typename Monoid::Type;

	const int level_m;		// 段数 - 1
	const size_t size_m;	// 1 << level_m
	std::vector<T> arr_m;

	static T identity();
	static T operate(const T& left, const T& right);
	bool isValidIndex(size_t pos) const;
	
	static const int Default = -1;

public:
	SegmentTree(int level);

	void update(size_t pos, const T& value);
	T query(size_t left, size_t right) const;
	T get(size_t pos) const;
	void debug(int level = Default, int cell_width = 4) const;
};

template<class Monoid>
typename SegmentTree<Monoid>::T SegmentTree<Monoid>::identity() {
	return Monoid::identity();
}

template<class Monoid>
typename SegmentTree<Monoid>::T SegmentTree<Monoid>::operate(const T& left, const T& right) {
	return Monoid::operate(left, right);
}

template<class Monoid>
inline bool SegmentTree<Monoid>::isValidIndex(size_t pos) const {
	return pos >= 0 && pos < size_m;
}

/* 1 << level 要素の segment tree_m を作成 */
template<class Monoid>
SegmentTree<Monoid>::SegmentTree(int level)
	: level_m(level), size_m(1 << level) {
	assert(level < 32);
	arr_m.resize(size_m * 2, identity());
}

/* pos 番目の要素を value に書き換える */
template<class Monoid>
void SegmentTree<Monoid>::update(size_t pos, const T& value) {
	pos += size_m;
	arr_m[pos] = value;
	pos >>= 1;
	while (pos > 0) {
		arr_m[pos] = operate(arr_m[pos * 2], arr_m[pos * 2 + 1]);
		pos >>= 1;
	}
}

/* [left, right) に存在する全要素の(指定した演算に関する)積をとる */
template<class Monoid>
typename SegmentTree<Monoid>::T SegmentTree<Monoid>::query(size_t left, size_t right) const {
	assert(left <= right);

	T tmp_left = identity();
	T tmp_right = identity();
	left += size_m;
	right += size_m;
	while (left < right) {
		if (left & 1) tmp_left = operate(tmp_left, arr_m[left++]);
		if (right & 1) tmp_right = operate(arr_m[--right], tmp_right);
		left >>= 1;
		right >>= 1;
	}

	return operate(tmp_left, tmp_right);
}

/* pos 番目の要素を直接取得 */
template<class Monoid>
typename SegmentTree<Monoid>::T SegmentTree<Monoid>::get(size_t pos) const {
	return arr_m[size_m + pos];
}

/* デバッグ出力用; level = -1 とすると全要素出力 */
template<class Monoid>
void SegmentTree<Monoid>::debug(int level, int cell_width) const {
	/* 値 value を幅 max_length になるように成形して文字列化 */
	auto to_str_fixed = [](const T& value, int max_length) -> std::string {
		std::ostringstream osst;
		osst << value;

		std::string str = osst.str();
		std::string output;
		if (str.size() > max_length) {
			for (int i = 0; i < max_length; ++i) {
				output += '#';
			}
		} else {
			const int remain_length = max_length - str.size();
			const int right_blank = remain_length / 2;
			const int left_blank = remain_length - right_blank;
			for (int i = 0; i < left_blank; ++i) {
				output += ' ';
			}
			output += str;
			for (int i = 0; i < right_blank; ++i) {
				output += ' ';
			}
		}
		return output;
	};

	if (level == Default) {			// デフォルト値への対処
		level = level_m;
	}

	if (level > level_m) {
		level = level_m;
	}

	std::vector<std::string> output_strs;

	for (int lev = 0; lev <= level; ++lev) {
		std::string output;
		const int front = size_m >> lev;

		output += '|';
		for (int i = 0; i < (1 << (level - lev)); ++i) {
			output += to_str_fixed(arr_m[front + i], cell_width);
			output += '|';
		}
		output_strs.push_back(output);

		cell_width = cell_width * 2 + 1;
	}

	reverse(output_strs.begin(), output_strs.end());
	for (const std::string& output : output_strs) {
		std::cout << output << std::endl;
	}
}

#endif

#define _CRT_SECURE_NO_WARNINGS
#define _SCL_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <utility>
#include <algorithm>
#include <functional>
#include <cmath>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <iomanip>
#include <sstream>
#include <bitset>
#include <limits>
#include <numeric>
#include <valarray>
#include <fstream>
#include <array>
#include <random>
#include <unordered_set>
#include <unordered_map>

using namespace std;
using uint = uint32_t;
using LL = int64_t;
using ULL = uint64_t;
using PP = pair<LL, LL>;
template <typename T> using PriorityQ = priority_queue<T, vector<T>, greater<T> >;
#define REP(i, a, n) for(LL i = (a), i##_max_ = (n); i < i##_max_; ++i)
#define REM(i, a, n) for(LL i = (LL)(n) - 1, i##_min_ = (a); i >= i##_min_; --i)
#define FLOAT fixed << setprecision(16)
#define SPEEDUP { cin.tie(NULL); ios::sync_with_stdio(false); }
const int INF = 0x3FFFFFFF;
const LL INFLL = 0x3FFFFFFF3FFFFFFF;
const double INFD = 1.0e+308;
const double EPS = 1.0e-9;

void YesNo(bool b) { cout << (b ? "Yes" : "No") << endl; }
void YESNO(bool b) { cout << (b ? "YES" : "NO") << endl; }
template <class T, class U> istream& operator>>(istream& ist, pair<T, U>& right) { return ist >> right.first >> right.second; }
template <class T, class U> ostream& operator<<(ostream& ost, const pair<T, U>& right) { return ost << right.first << ' ' << right.second; }
template <class T, class TCompatible, size_t N> void Fill(T(&dest)[N], const TCompatible& val) { fill(dest, dest + N, val); }
template <class T, class TCompatible, size_t M, size_t N> void Fill(T(&dest)[M][N], const TCompatible& val) { for (int i = 0; i < M; ++i) Fill(dest[i], val); }
template <class T> T Next() { T buf; cin >> buf; return buf; }
istream& Ignore(istream& ist) { string s; ist >> s; return ist; }
bool Inside(int i, int j, int h, int w) { return i >= 0 && i < h && j >= 0 && j < w; }

#ifdef ONLY_MY_ENVIR
#include "Accumulator.h"
#include "Algebraic.h"
#include "BinaryMatrix.h"
#include "BinaryTree.h"
#include "Bipartite.h"
#include "BIT.h"
#include "Compressor.h"
#include "Decompositions.h"
#include "DynamicMod.h"
#include "Factorization.h"
#include "FFT.h"
#include "FlowSolver.h"
#include "Graph.h"
#include "GraphUtil.h"
#include "IntMod.h"
#include "LazySegmentTree.h"
#include "LIS.h"
#include "Math.h"
#include "MathUtil.h"
#include "Matrix.h"
#include "MinCostFlowSolver.h"
#include "MinMax.h"
#include "Numbers.h"
#include "Optimize.h"
#include "Permutation.h"
#include "Polynomial.h"
#include "Position.h"
#include "Range.h"
#include "Rational.h"
#include "SegmentTree.h"
#include "SegmentTree2D.h"
#include "Sets.h"
#include "Shortest.h"
#include "SlidingWindow.h"
#include "SpanningTree.h"
#include "StringSearching.h"
#include "SuffixArray.h"
#include "Tree.h"
#include "TreeUtil.h"
#include "UnionFind.h"
#include "Util.h"
#include "VectorUtil.h"
#endif

#ifdef __GNUC__
typedef __int128 LLL;
istream& operator>>(istream& ist, __int128& val) { LL tmp; ist >> tmp; val = tmp; return ist; }
ostream& operator<<(ostream& ost, __int128 val) { LL tmp = val; ost << tmp; return ost; }
#endif

int N, M;
LL A[5000];
SegmentTree<Monoid::Maximum<PP>>* segs[200];
LL P[5002][5002];

LL post() {
	REP(i, 0, N + 1) {
		REP(j, 0, N + 1) {
			P[i + 1][j + 1] += P[i + 1][j] + P[i][j + 1] - P[i][j];
		}
	}

	LL mx = 0;
	REP(i, 0, N) {
		REP(j, i, N) {
			mx = max(mx, P[i + 1][j + 1] - (A[j] - A[i]));
		}
	}
	return mx;
}

void add(LL val, int li, int lj, int ri, int rj) {
	P[li + 1][lj + 1] += val;
	P[li + 1][rj + 1] -= val;
	P[ri + 1][lj + 1] -= val;
	P[ri + 1][rj + 1] += val;
}

void rec(int i, int l, int r) {
	if (l == r) return;
	PP mxp = segs[i]->query(l, r);
	LL val = mxp.first;
	int mxi = mxp.second;

	add(val, l, mxi, mxi + 1, r);

	rec(i, l, mxi);
	rec(i, mxi + 1, r);
}

void sub(int i) {
	rec(i, 0, N);
}

int main() {
	cin >> N >> M;
	LL sum = 0;
	REP(i, 1, N) {
		sum += Next<LL>();
		A[i] = sum;
	}

	REP(i, 0, M) {
		segs[i] = new SegmentTree<Monoid::Maximum<PP>>(13);
	}

	REP(j, 0, N) {
		REP(i, 0, M) {
			segs[i]->update(j, PP(Next<LL>(), j));
		}
	}

	REP(i, 0, M) {
		sub(i);
	}

	cout << post() << endl;

	REP(i, 0, M) {
		delete segs[i];
	}

	return 0;
}



Measured memory_bytes: 247808