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)
}

Python: while 1:
    D,W=list(map(int,input().split()))
    if (D,W)==(0,0):
        break
    garden = [list(map(int,input().split())) for _ in range(D)]
    ans=0
    for wi in range(W):
        for wj in range(wi+2,W):
            for di in range(D):
                for dj in range(di+2,D):
                    edge_min = float("inf")
                    water_sum=0
                    count=0
                    in_max=0
                    for w in range(wi,wj+1):
                        for d in range(di,dj+1):
                            if w in (wi,wj) or d in (di,dj) :
                                edge_min= min(garden[d][w] , edge_min)
                                ###print(edge_min,garden[d][w],"eee",min(edge_min,garden[d][w]))
                            else:
                                water_sum+=garden[d][w]
                                in_max=max(in_max,garden[d][w])
                                count+=1
                    if edge_min>in_max:                    
                        ans=max(ans,edge_min*count - water_sum)
    print(ans)

Python: while 1:
    d, w = map(int, input().split())
    if d==w==0:
        break
    E=[list(map(int, input().split())) for i in range(d)]
    a=0
    for x2 in range(d):
        for y2 in range(w):
            for x1 in range(x2-1):
                for y1 in range(y2-1):
                    co=10**18
                    for x in range(x1, x2+1):
                        co=min(co, E[x][y1], E[x][y2])
                    for y in range(y1, y2+1):
                        co=min(co, E[x1][y], E[x2][y])
                    ci=cnt=0
                    for x in range(x1+1, x2):
                        for y in range(y1+1, y2):
                            ci=max(ci, E[x][y])
                            cnt+=E[x][y]
                    if ci < co:
                        a=max(ans, (x2-x1-1)*(y2-y1-1)*co - cnt)
    print(a)

Python: while 1:
    d, w = map(int, input().split())
    if d == w == 0:
        break
    E = [0]*d
    for i in range(d):
        *E[i], = map(int, input().split())
    ans = 0
    for x2 in range(d):
        for y2 in range(w):
            for x1 in range(x2-1):
                for y1 in range(y2-1):
                    co = 10**18
                    for x in range(x1, x2+1):
                        co = min(co, E[x][y1], E[x][y2])
                    for y in range(y1, y2+1):
                        co = min(co, E[x1][y], E[x2][y])
                    ci = cnt = 0
                    for x in range(x1+1, x2):
                        for y in range(y1+1, y2):
                            ci = max(ci, E[x][y])
                            cnt += E[x][y]
                    if ci < co:
                        ans = max(ans, (x2-x1-1)*(y2-y1-1)*co - cnt)
    print(ans)

Python: while 1:
    d, w = map(int, input().split())
    if d == w == 0:
        break
    E = [[*map(int, input().split())] for i in range(d)]
    ans = 0
    for x2 in range(d):
        for y2 in range(w):
            for x1 in range(x2-1):
                for y1 in range(y2-1):
                    # [x1, x2] x [y1, y2]
                    co = 10**18
                    for x in range(x1, x2+1):
                        co = min(co, E[x][y1], E[x][y2])
                    for y in range(y1, y2+1):
                        co = min(co, E[x1][y], E[x2][y])
                    ci = 0
                    cnt = 0
                    for x in range(x1+1, x2):
                        for y in range(y1+1, y2):
                            ci = max(ci, E[x][y])
                            cnt += E[x][y]
                    if ci < co:
                        ans = max(ans, (x2-x1-1)*(y2-y1-1)*co - cnt)
    print(ans)

Python: while(True):
	h, w = map(int, input().split())
	if (h+w) == 0:break
	e = list(list(int(i) for i in input().split()) for i in range(h))
	e_T = list(zip(*e))
	ans = 0
	for i in range(h-2):
		for j in range(w-2):
			for k in range(i+2,h):
				for l in range(j+2,w):
					flag = False
					count = 0
					wall = min(min(e[i][j:l+1]), min(e[k][j:l+1]), min(e_T[j][i:k+1]), min(e_T[l][i:k+1]))
					#print(wall)
					for m in range(i+1,k):
						for n in range(j+1,l):
							if wall > e[m][n]:
								count += wall - e[m][n]
							else:
								flag = True
								break
						if flag:break
					
					if ans < count and not flag:
						ans = count				
	print(ans)