#include<bits/stdc++.h>
using namespace std;
#define N 2005
#define F first
#define S second
int n,m,A[N][N],a[N][N],dp[N][N],ans=2e9;
typedef pair<int,int> pa;
pa cal(int n,int m,int v){
memset(dp,0,sizeof dp);
for(int i=0;i<=n;i++) dp[i][0] = 1;
for(int i=0;i<=m;i++) dp[0][i] = 1;
for(int i=1;i<=m;i++) for(int j=1;j<=n;j++) if(a[j][i] <= v && dp[j][i-1] && dp[j-1][i]) dp[j][i] = 1;
int mx0=0,mx1=0,mn0=1e9,mn1=1e9;
for(int i=1;i<=n;i++) for(int j=1;j<=m;j++){
if(!dp[i][j]) mx0 = max(mx0,a[i][j]), mn0 = min(mn0,a[i][j]);
else mx1 = max(mx1,a[i][j]), mn1 = min(mn1,a[i][j]);
}
if(!dp[1][1]) return {0,2e9};
if(dp[n][m]) return {2e9,0};
if(mn1 >= mn0) return {2e9,0};
// printf(">> %d : %d %d %d %d\n",v,mx1,mn1,mx0,mn0);
return {mx1-mn1,mx0-mn0};
}
int sol(int n,int m){
int be = 0,ed = 1e9+1,ans=2e9;
while(ed - be > 1){
int mid = (be+ed)/2;
pa V = cal(n,m,mid);
ans = min(ans,max(V.F,V.S));
// printf("%d : %d %d\n",mid,V.F,V.S);
if(V.F <= V.S) be = mid;
else ed = mid;
}
return ans;
}
int main(){
scanf("%d%d",&n,&m);
for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) scanf("%d",&A[i][j]);
for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) a[i][j] = A[i][j];
ans = min(ans,sol(n,m));
for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) a[n-i+1][j] = A[i][j];
ans = min(ans,sol(n,m));
for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) a[m-j+1][n-i+1] = A[i][j];
ans = min(ans,sol(m,n));
for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) a[j][n-i+1] = A[i][j];
ans = min(ans,sol(m,n));
printf("%d",ans);
}
/*
4 4
1 12 6 11
11 10 2 14
10 1 9 20
4 17 19 10
3 4
1 1 1 1
1 1 9 2
2 2 2 2
3 4
2 2 2 2
9 2 1 1
1 1 1 1
*/
