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 <stdio.h>

int max(int a, int b){
  if (a > b) {
    return a;
  } else {
    return b;
  }
}
int min(int a, int b ){
  if (a > b) {
    return b;
  } else {
    return a;
  }
}

int main(void){
  int d,w;
  int stage[10][10];
  int counter;
  int frmin;
  int depsum,depmax;
  int depsummax;
  //int allsum[10][10];
  scanf("%d%d",&d,&w );
  while (d != 0) {
    for (int i = 0; i < d; i++) {
      for (int j = 0; j < w; j++) {
        scanf("%d",&stage[i][j]);
        //allsum[i][j] = 0
      }
    }

    depsummax = 0;
    /*
    for (int i = 1; i < d+1; i++) {
      for (int j = 1; j < w+1; j++) {
        allsum[i][j] = allsum[i][j-1] + stage[i-1][j-1];
      }
    }
    for (int i = 1; i < w+1; i++) {
      for (int j = 1; j < d+1; j++) {
        allsum[j][i] = allsum[j-1][i] + stage[j-1][i-1];
      }
    }
    */
    for (int i = 0; i < d-2; i++) {
      for (int j = 0; j < w-2; j++) { //始点
        for (int k = i+2; k < d; k++) {
          for (int l = j+2; l < w; l++) { // 終点
            depmax = 0;
            depsum = 0;
            frmin = 1000;
            counter = 0; //initialize
            for (int m = i; m <= k; m++) {
              for (int n = j; n <= l; n++) {
                if (i<m&&m<k && j<n&&n<l) {
                  depsum += stage[m][n];
                  counter++;
                  depmax = max(depmax,stage[m][n]);
                } else {
                  frmin = min(frmin,stage[m][n]);
                }
              }
            }
            if (depmax < frmin) {
              depsum = frmin * counter - depsum;
              depsummax = max(depsummax,depsum);
            }
          }
        }
      }
    }
    
    printf("%d\n",depsummax );
    scanf("%d%d", &d,&w);
  }
  return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL,LL> P;
const LL mod=1e9+7;
const LL LINF=1LL<<62;
const int INF=1<<17;

int main(){
    int d,w;
    while(cin >> d >> w){
        if(d==0&&w==0) break;
        int st[d][w];
        for(int i=0;i<d;i++){
            for(int j=0;j<w;j++){
                cin >> st[i][j];
            }
        }
        int ans=0;
        for(int i=0;i<d;i++){
            for(int j=0;j<w;j++){
                for(int y=3;y<=d;y++){
                    for(int x=3;x<=w;x++){
                        int mini=INF,maxi=-1;
                        if(d<i+y||w<j+x) continue;
                        int sum=0;
                        for(int s=0;s<y;s++){
                            for(int t=0;t<x;t++){
                                if(s==0||s==y-1||t==0||t==x-1){
                                    mini=min(mini,st[i+s][j+t]);
                                }
                                else{
                                    sum+=st[i+s][j+t];
                                    maxi=max(maxi,st[i+s][j+t]);
                                }
                            }
                        }
                    if(maxi<mini) ans=max(ans,mini*(x-2)*(y-2)-sum);
                    }
                }
            }
        }
        cout << ans << endl;
    }
    return 0;
}