#include <bits/stdc++.h>
#define DIM 2010
#define DIMBUFF 30000000
#define INF 2000000000
using namespace std;
int a[DIM][DIM],b[DIM][DIM],viz[DIM][DIM];
struct idk{
int val,l,c;
} v[DIM*DIM];
pair<int,int> c[DIM*DIM];
int di[] = {-1,1,0,0};
int dj[] = {0,0,-1,1};
int n,m,i,j,sol,mini,maxi,k,pos;
char buff[DIMBUFF];
int verif (int val){
int last = 0;
for (i=1;i<=n;i++){
for (j=1;j<=m;j++){
if (a[i][j] < maxi - val)
last = max(last,j);
}
for (j=1;j<=m;j++)
if (a[i][j] > mini + val && j <= last)
return 0;
}
return 1;
}
void solve (){
int st = 0, dr = maxi - mini, val = INF;
while (st <= dr){
int mid = (st+dr)>>1;
if (verif (mid)){
val = mid;
dr = mid-1;
} else st = mid+1;
}
sol = min (sol,val);
}
inline int cmp (idk a, idk b){
return a.val < b.val;
}
void roteste_linii(){
for (i=1;i<=n/2;i++)
for (j=1;j<=m;j++)
swap (a[i][j],a[n-i+1][j]);
}
void roteste_coloane(){
for (i=1;i<=n;i++)
for (j=1;j<=m/2;j++)
swap (a[i][j],a[i][m-j+1]);
}
int get_nr(){
while (!(buff[pos] >= '0' && buff[pos] <= '9'))
++pos;
int nr = 0;
while (buff[pos] >= '0' && buff[pos] <= '9'){
nr = nr*10 + buff[pos] - '0';
++pos;
}
return nr;
}
int main (){
//ifstream cin ("date.in");
//ofstream cout ("date.out");
cin>>n>>m;
mini = INF;
for (i=1;i<=n;++i)
for (j=1;j<=m;++j){
cin>>a[i][j];
mini = min (mini,a[i][j]);
maxi = max (maxi,a[i][j]);
// v[++k] = {a[i][j],i,j};
}
//sort (v+1,v+k+1,cmp);
sol = INF;
solve();
roteste_linii();
solve();
roteste_coloane();
solve();
roteste_linii();
solve();
cout<<sol;
return 0;
}
