/* 
 * Problem: POI1999 wod
 * Author: Guo Jiabao
 * Time: 2008.12.16 21:44:50
 * State: Solved 
*/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>

using namespace std;

const int MAX=101;
const int dx[4]={0,0,-1,1},dy[4]={1,-1,0,0};

struct point
{
	int x,y;
};

int N,M,All;
int Alt[MAX][MAX];
bool vid[MAX][MAX];
int heap_size;
point Heap[MAX*MAX];

void heap_ins(int x,int y)
{
	int i;
	for (i=++heap_size;Alt[x][y]<Alt[Heap[i/2].x][Heap[i/2].y];i=i/2)
		Heap[i]=Heap[i/2];
	Heap[i].x=x; Heap[i].y=y;
}

point heap_delmin()
{
	point R=Heap[1],M=Heap[heap_size--];
	int i,c;
	for (i=1;i*2<=heap_size;i=c)
	{
		c=i*2;
		if (c!=heap_size && Alt[Heap[c+1].x][Heap[c+1].y]<Alt[Heap[c].x][Heap[c].y])
			c++;
		if (Alt[M.x][M.y] > Alt[Heap[c].x][Heap[c].y])
			Heap[i]=Heap[c];
		else
			break;
	}
	Heap[i]=M;
	return R;
}

void init()
{
	freopen("wod.in","r",stdin);
	freopen("wod.out","w",stdout);
	scanf("%d%d",&N,&M);
	for (int i=1;i<=N;i++)
		for (int j=1;j<=M;j++)
			scanf("%d",&Alt[i][j]);
	Alt[0][0]=-0x7FFFFFFF;
	Heap[heap_size=0].x=Heap[0].y=0;
}

inline bool inrange(point A)
{
	return A.x>=1 && A.x<=N && A.y>=1 && A.y<=M;
}

void floodfill(point A,int h)
{
	point B;
	vid[A.x][A.y]=true;
	if (Alt[A.x][A.y]>=h)
		heap_ins(A.x,A.y);
	else
	{
		All+=h-Alt[A.x][A.y];
		for (int i=0;i<4;i++)
		{
			B.x=A.x+dx[i]; B.y=A.y+dy[i];
			if (inrange(B) && !vid[B.x][B.y])
				floodfill(B,h);
		}
	}
}

void solve()
{
	int i,j;
	point A,B;
	for (i=1;i<=N;i++)
	{
		heap_ins(i,1);
		heap_ins(i,M);
		vid[i][1]=vid[i][M]=true;
	}
	for (i=2;i<=M-1;i++)
	{
		heap_ins(1,i);
		heap_ins(N,i);
		vid[1][i]=vid[N][i]=true;
	}
	while (heap_size)
	{
		A=heap_delmin();
		for (i=0;i<4;i++)
		{
			B.x=A.x+dx[i]; B.y=A.y+dy[i];
			if (inrange(B) && !vid[B.x][B.y])
				floodfill(B,Alt[A.x][A.y]);
		}
	}
}

int main()
{
	init();
	solve();
	printf("%d",All);
	return 0;
}