Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		d, w := io.NextInt(), io.NextInt()
		if d == 0 {
			break
		}
		e := make([][]int, d)
		for i := 0; i < d; i++ {
			e[i] = make([]int, w)
			for j := 0; j < w; j++ {
				e[i][j] = io.NextInt()
			}
		}
		ans := 0
		for i := 0; i < d-2; i++ {
			for j := 0; j < w-2; j++ {
				for k := i + 2; k < d; k++ {
					for l := j + 2; l < w; l++ {
						ans = intMax(vol(e, i, j, k, l), ans)
					}
				}
			}
		}
		io.Println(ans)
	}
}

func vol(e [][]int, a, b, c, d int) int {
	outer := 10
	for i := a; i <= c; i++ {
		outer = intMin(e[i][b], outer)
		outer = intMin(e[i][d], outer)
	}
	for j := b; j <= d; j++ {
		outer = intMin(e[a][j], outer)
		outer = intMin(e[c][j], outer)
	}
	a++
	b++
	vol := 0
	for i := a; i < c; i++ {
		for j := b; j < d; j++ {
			if e[i][j] >= outer {
				return 0
			}
			vol += outer - e[i][j]
		}
	}
	return vol
}

func intMax(a, b int) int {
	if a < b {
		return b
	}
	return a
}

func intMin(a, b int) int {
	if a > b {
		return b
	}
	return a
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
using namespace std;



int main(){

while(1){
    int d,w;
    cin >> d >>w;
    if(d==0 && w==0)break;
    int ground[d][w];
    for(int i=0;i<d;i++){
        for(int j=0;j<w;j++){
            cin >>ground[i][j];
        }
    }
    int ans=0;
    vector<int> lake(0);
    vector<int> wall(0);
    for(int dstart=0;dstart<d-2;dstart++){
        for(int dend=dstart+2;dend<d;dend++){
            for(int wstart=0;wstart<w-2;wstart++){
                for(int wend=wstart+2;wend<w;wend++){
                    lake.clear();
                    wall.clear();
                    for(int dd=dstart;dd<=dend;dd++){
                        for(int ww=wstart;ww<=wend;ww++){
                            if(dd==dstart || dd==dend || ww==wstart|| ww==wend){
                                wall.push_back(ground[dd][ww]);
                            }
                            else lake.push_back(ground[dd][ww]);
                        }
                    }
                    if(wall.size()!=0)sort(wall.begin(),wall.end());
                    if(lake.size()!=0){
                        sort(lake.begin(),lake.end());
                        reverse(lake.begin(),lake.end());
                        }
                    int temp=0;
                    for(int pl=0;pl<lake.size();pl++)temp+=(wall[0]-lake[pl]);
                    if(wall[0]<=lake[0])temp=0;
                    ans=max(ans,temp);
                }
            }
        }
    }
    cout << ans <<endl;
    }

}

C++: #include<bits/stdc++.h>
using namespace std;

int solve(int h,int w){
    vector<vector<int>> e(h,vector<int>(w));
    for(int i=0;i<h;i++) for(int j=0;j<w;j++) cin>>e[i][j];
    int res=0;
    auto calc=[&](int t,int b,int l,int r){
        int wall=10;
        for(int i=l;i<=r;i++){
            wall=min(wall,e[t][i]);
            wall=min(wall,e[b][i]);
        }
        for(int i=t;i<=b;i++){
            wall=min(wall,e[i][l]);
            wall=min(wall,e[i][r]);
        }
        int res=0;
        for(int i=t+1;i<b;i++){
            for(int j=l+1;j<r;j++){
                if(wall>e[i][j]) res+=wall-e[i][j];
                else return 0;
            }
        }
        return res;
    };
    for(int t=0;t<h;t++){
        for(int b=t+2;b<h;b++){
            for(int l=0;l<w;l++){
                for(int r=l+2;r<w;r++){
                    res=max(res,calc(t,b,l,r));
                }
            }
        }
    }
    return res;
}

int main(){
    int h,w;
    while(cin>>h>>w,h){
        cout<<solve(h,w)<<endl;
    }
    return 0;
}

C++: #include <stdio.h>
#include <cmath>
#include <algorithm>
#include <cfloat>
#include <stack>
#include <queue>
#include <vector>
typedef long long int ll;
#define BIG_NUM 2000000000
#define MOD 1000000007
#define EPS 0.000001
using namespace std;

int H,W;

int main(){

	int maximum,map[10][10],tmp_sea_max,tmp_wall_min,tmp;

	while(true){
		scanf("%d %d",&H,&W);
		if(H == 0 && W == 0)break;

		for(int i = 0; i < H; i++){
			for(int k = 0; k < W; k++)scanf("%d",&map[i][k]);
		}

		maximum = 0;

		for(int sea_left = 1; sea_left <= W-2; sea_left++){
			for(int sea_right = sea_left; sea_right <= W-2; sea_right++){
				for(int sea_top = 1; sea_top <= H-2; sea_top++){
					for(int sea_bottom = sea_top; sea_bottom <= H-2; sea_bottom++){

						tmp_sea_max = 0;
						for(int row = sea_top;row <= sea_bottom;row++){
							for(int col = sea_left; col <= sea_right; col++){
								tmp_sea_max = max(tmp_sea_max,map[row][col]);
							}
						}

						tmp_wall_min = 100;
						for(int col = sea_left-1;col <= sea_right+1; col++)tmp_wall_min = min(tmp_wall_min,map[sea_top-1][col]);
						for(int col = sea_left-1;col <= sea_right+1; col++)tmp_wall_min = min(tmp_wall_min,map[sea_bottom+1][col]);
						for(int row = sea_top-1; row <= sea_bottom+1;row++)tmp_wall_min = min(tmp_wall_min,map[row][sea_left-1]);
						for(int row = sea_top-1; row <= sea_bottom+1;row++)tmp_wall_min = min(tmp_wall_min,map[row][sea_right+1]);

						if(tmp_sea_max >= tmp_wall_min)continue;

						tmp = 0;
						for(int row = sea_top;row <= sea_bottom;row++){
							for(int col = sea_left; col <= sea_right; col++){
								tmp += tmp_wall_min-map[row][col];
							}
						}

						maximum = max(maximum,tmp);
					}
				}
			}
		}

		printf("%d\n",maximum);

	}

	return 0;
}