//new.cpp
/*
Author : Hocky Yudhiono
Sen 15 Apr 2019 04:06:13  WIB
Current Local Time : 16:06:13

getchar_unlocked > getchar > cin without sync > scanf > cin with sync
bool operator<(const MyStruct& rhs) const

On how to print Long Double to 5 decimal places :
printf("%.5Lf",ans);

On how to get random numbers :
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); //For int
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()); //For LL
cout << rng() << endl;
shuffle(isi.begin(),isi.end(),rng);

__gcd(a,b)
__builtin_ffs(a) first on bit
__builtin_clz(a) count leading zero
__builtin_ctz(a) count trailing zero
__builtin_popcount(a) numbers of on bits

*/

//#include <unordered_map>
//#include <unordered_set>

//#include <random>
//#include <chrono>

//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>

#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cassert>
#include <cstring>
#include <iomanip>
#include <cstdio>
#include <limits>
#include <string>
#include <vector>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <map>
#include <set>

//using namespace __gnu_pbds;
using namespace std;

#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize(3)
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC target("sse3","sse2","sse")
#pragma GCC target("avx","sse4","sse4.1","sse4.2","ssse3")
#pragma GCC target("f16c")
#pragma GCC optimize("inline","fast-math","unroll-loops","no-stack-protector")
// #pragma GCC diagnostic error "-fwhole-program"
// #pragma GCC diagnostic error "-fcse-skip-blocks"
// #pragma GCC diagnostic error "-funsafe-loop-optimizations"
// #pragma GCC diagnostic error "-std=c++14"
// #pragma GCC target ("string"...)
#pragma GCC push_options
#pragma GCC pop_options
#pragma GCC reset_options
#pragma GCC optimize ("O3")

typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
// typedef tree<long long, null_type, less<long long>, rb_tree_tag, tree_order_statistics_node_update> pbds;
//If the time limit is strict, try not to use long double


#define fbo find_by_order
#define ook order_of_key
#define mp make_pair
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define remove erase
//Remember to undefine if the problem is interactive
#define endl '\n'
#define DEBUG(X) cout << ">>> DEBUG(" << __LINE__ << ") " << #X << " = " << (X) << endl

const double eps = 1e-9;
const int INFMEM = 63;
const int INF = 1061109567;
const LL LINF = 4557430888798830399LL;
const double DINF = numeric_limits<double>::infinity();
const LL MOD = 1000000007;
const int dx[8] = {1,0,-1,0,1,1,-1,-1};
const int dy[8] = {0,1,0,-1,1,-1,1,-1};
const double PI = 3.141592653589793;

#ifdef _WIN32
#define getchar_unlocked getchar
#endif
#define GETCHAR getchar_unlocked
inline void fastll(LL &input_number) 
{
    input_number = 0;
    int ch = GETCHAR();
    int sign = 1;
    while(ch < '0' || ch > '9'){
        if(ch == '-') sign=-1;
        ch = GETCHAR();
    }
    while(ch >= '0' && ch <= '9'){
        input_number = (input_number << 3)+(input_number << 1) + ch-'0';
        ch = GETCHAR();
    }
    input_number *= sign;
}

inline void open(string a){
    freopen((a+".in").c_str(),"r",stdin);
    freopen((a+".out").c_str(),"w",stdout);
}

inline void fasterios(){
    //Do not use if interactive
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
}

LL n,m;
LL a[5005];
LL kiri[5005];
LL kanan[5005];
stack <LL> cur;
LL isi[5005][205];
LL sum[5005][5005];

int main(){
    cin >> n >> m;
    for(int i = 2;i <= n;i++){
    	cin >> a[i]; a[i] += a[i-1];
    }
    for(int i = 1;i <= n;i++){
    	for(int j = 1;j <= m;j++){
    		cin >> isi[i][j];
    	}
    }
    for(int i = 1;i <= m;i++){
    	for(int j = 1;j <= n;j++) kiri[j] = kanan[j] = 0;
    	while(!cur.empty()) cur.pop();
    	for(int j = 1;j <= n;j++){
    		while(!cur.empty() && isi[j][i] > isi[cur.top()][i]) cur.pop();
    		LL now;
    		if(cur.empty()) now = 1;
    		else now = cur.top()+1;
    		kiri[j] = now;
    		cur.push(j);
    	}
    	while(!cur.empty()) cur.pop();
    	for(int j = n;j >= 1;j--){
    		while(!cur.empty() && isi[j][i] > isi[cur.top()][i]) cur.pop();
    		LL now;
    		if(cur.empty()) now = n;
    		else now = cur.top()-1;
    		kanan[j] = now;
    		cur.push(j);
    	}
    	//		Lets say were in a current restaurant, will use this current restaurant, what is the left most and rightmost point
    	
		//    	kiri.x ,kiri.y kanan.x kanan.y
		//    	sum[kiri.x][kiri.y] +=
		//    	sum[kiri.x][kanan.y+1] -=
		//    	sum[kanan.x+1][kiri.y] -=
		//    	sum[kanan.x+1][kanan.y+1] += 
    	//		kiri[j] = batas terkiri jika restoran ini masuk, pada segment, 
    	for(int j = 1;j <= n;j++){
//    		cout << i << "-th meal tickets" << " ------ " << j << "-th restaurant " << kiri[j] << " " << kanan[j] << endl;
    		//	prefix difference 2d
    		sum[kiri[j]][j] += isi[j][i];
    		sum[kiri[j]][kanan[j]+1] -= isi[j][i];
    		
			sum[j+1][kanan[j]+1] += isi[j][i];
    		sum[j+1][j] -= isi[j][i];
    	
		}
    }
    LL ans = 0;
    for(int i = 1;i <= n;i++){
    	for(int j = 1;j <= n;j++){
    		sum[i][j] += sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1];
    		if(i > j){
//    			cout << sum[i][j] << " \n"[j == n];
				continue;	
    		}
    		ans = max(ans,sum[i][j]-(a[j]-a[i]));
//    		cout << sum[i][j] << " \n"[j == n];
    	}
    }
    cout << ans << endl;
    return 0;
}

Measured memory_bytes: 204032