#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2000;
const int MAXROT = 4;
int altitude[MAXROT][MAXN][MAXN];
int nbLig, nbCol;
int petit(1e9), grand(0);
bool isOk(int iRot, int deltaMax)
{
int prv(nbCol-1);
for (int iLig(0); iLig < nbLig; ++iLig)
{
int curCol(-1);
while (curCol + 1 <= prv and altitude[iRot][iLig][curCol+1] <= petit + deltaMax)
++curCol;
prv = curCol;
if (prv == -1 and !iLig)
return false;
for (int iCol=curCol+1; iCol < nbCol; ++iCol)
if (altitude[iRot][iLig][iCol] < grand - deltaMax)
return false;
}
return true;
}
bool can(int delta)
{
for (int iRot = 0; iRot < MAXROT; ++iRot)
if (isOk(iRot, delta))
return true;
return false;
}
signed main(void)
{
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> nbLig >> nbCol;
for (int iLig = 0; iLig < nbLig; ++iLig)
for (int iCol = 0; iCol < nbCol; ++iCol)
cin >> altitude[0][iLig][iCol];
for (int iLig = 0; iLig < nbLig; ++iLig)
for (int iCol = 0; iCol < nbCol; ++iCol)
{
altitude[1][iLig][iCol] = altitude[0][iLig][nbCol - iCol-1];
altitude[2][iLig][iCol] = altitude[0][nbLig-iLig-1][iCol];
altitude[3][iLig][iCol] = altitude[0][nbLig-iLig-1][nbCol-iCol-1];
}
for (int iLig = 0; iLig < nbLig; ++iLig)
for (int iCol = 0; iCol < nbCol; ++iCol)
petit = min(petit, altitude[0][iLig][iCol]),
grand = max(grand, altitude[0][iLig][iCol]);
int lo(0), up(1e9);
while (lo < up)
{
int mid = (lo + up)/2;
if (can(mid))
up = mid;
else
lo = mid + 1;
}
cout << lo << endl;
}
