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 <bits/stdc++.h>
using namespace std;

int dx[9] = {0, 0, 1, 1, 1, 0, -1, -1, -1}, dy[9] = {0, -1, -1, 0, 1, 1, 1, 0, -1};

int main() {
  int d, w;
  while ( cin >> d >> w, d ) {
    int e[d][w];
    for ( int i = 0; i < d; i++ ) {
      for ( int j = 0; j < w; j++ ) {
	cin >> e[i][j];
      }
    }

    int ans = 0;    
    for ( int a = 1; a <= 9; a++ ) {
      for ( int i = 1; i < d-1; i++ ) {
	for ( int j = 1; j < w-1; j++ ) {
	  if ( e[i][j] >= a ) continue;
	  int y = i, x = j;
	  while ( y+1 < d-1 && e[y+1][j] < a ) y++;
	  while ( x+1 < w-1 && e[i][x+1] < a ) x++;
	  bool flag = true;
	  int sum = 0;
	  // if ( a == 2 ) cout << i << j << y << x << endl;
	  for ( int r = i; r <= y; r++ ) {
	    for ( int c = j; c <= x; c++ ) {
	      sum += a-e[r][c];	      
	      for ( int k = 0; k < 9; k++ ) {	      
		int ny = r+dy[k], nx = c+dx[k];
		if ( k == 0 && e[ny][nx] >= a ) {		  
		  flag = false;
		  r = y; c = x; break;		  
		}
		if ( (ny < i || y < ny || nx < j || x < nx) && e[ny][nx] < a ) {
		  flag = false;
		  r = y; c = x; break;		  
		}
	      }	      
	    }
	  }
	  if ( flag ) {
	    ans = max(ans, sum);
	    // if ( sum == 22 ) cout << i << " " << j << " " << a << endl;
	  }	  
	}
      }
    }

    cout << ans << endl;
  }
  
  return 0;
}

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

int main(){
    
    for(int h, w; cin >> h >> w, h;){
        int mp[10][10];
        for(int y = 0; y < h; y++){
            for(int x = 0; x < w; x++){
                cin >> mp[y][x];
            }
        }
        int ans = 0;
        for(int y1 = 0; y1 < h; y1++){
            for(int x1 = 0; x1 < w; x1++){
                for(int y2 = y1 + 2; y2 < h; y2++){
                    for(int x2 = x1 + 2; x2 < w; x2++){
                        int mn = 9;
                        for(int x = x1; x <= x2; x++){
                            mn = min(mn, mp[y1][x]);
                            mn = min(mn, mp[y2][x]);
                        }
                        for(int y = y1; y <= y2; y++){
                            mn = min(mn, mp[y][x1]);
                            mn = min(mn, mp[y][x2]);
                        }
                        int cnt[10] = {};
                        for(int y = y1 + 1; y < y2; y++){
                            for(int x = x1 + 1; x < x2; x++){
                                cnt[mp[y][x]]++;
                            }
                        }
                        int tmp = 0;
                        for(int i = 0; i <= 9; i++){
                            if(cnt[i]){
                                if(mn <= i)tmp -= 1000000;
                                else tmp += cnt[i] * (mn - i);
                            }
                        }
                        ans = max(ans, tmp);
                    }
                }
            }
        }
        cout << ans << endl;
    }

    return 0;
}

C++: #include<iostream>
#include<cstdio>
using namespace std;
int n,m,a[15][15],cnt,ans[105];

int main()
{
		scanf("%d %d",&n,&m);
	while(n||m)
	{
		++cnt;
		for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++)
		scanf("%d",&a[i][j]);
		for(int i=2;i<=n-1;i++)
		for(int j=2;j<=m-1;j++)
		for(int k=i;k<=n-1;k++)
		for(int h=j;h<=m-1;h++){
			int miny=2e9,maxy=-1,sum=0;
			for(int ii=i;ii<=k;ii++)
			for(int jj=j;jj<=h;jj++){
				maxy=max(maxy,a[ii][jj]);
				sum+=9-a[ii][jj];
			}
			for(int ii=i-1;ii<=k+1;ii++)miny=min(miny,min(a[ii][j-1],a[ii][h+1]));
			for(int jj=j;jj<=h;jj++)miny=min(miny,min(a[i-1][jj],a[k+1][jj]));
			if(maxy<miny)ans[cnt]=max(ans[cnt],sum-(9-miny)*(k-i+1)*(h-j+1));
		}
		scanf("%d %d",&n,&m);
	}
	for(int i=1;i<=cnt;i++)printf("%d\n",ans[i]);
 }

C++: #include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,a,b) for(int i=a;i<=b;i++)
using namespace std;
int main(){
	while(1){
		int d,w;
		cin>>d>>w;
		if(!d)break;
		int e[d][w];
		rep(i,d)rep(j,w)cin>>e[i][j];
		int ans=0;
		rep(i,d){
			rep(j,w){
				REP(k,i+2,d-1){
					REP(l,j+2,w-1){
						int a=10;
						REP(m,i,k)a=min(a,min(e[m][j],e[m][l]));
						REP(m,j,l)a=min(a,min(e[i][m],e[k][m]));
						int b=0;
						REP(m,i+1,k-1){
							REP(n,j+1,l-1){
								b=max(b,e[m][n]);
							}
						}
						if(a>b){
							int t=0;
							REP(m,i+1,k-1){
								REP(n,j+1,l-1){
									t+=a-e[m][n];
								}
							}
							ans=max(ans,t);
						}
					}
				}
			}
		}
		cout<<ans<<endl;
	}
	return 0;
}