#include <iostream>
#include <iomanip>
using namespace std;
#define INF 1000000001
int n, m, i, j, a[2010][2010], ao[2010][2010], av[2010][2010], ac[2010][2010];
int mini = INF, maxi = 0, st, dr, mij, sol;
bool testDiff (int x, int (&a)[2010][2010])
{
int prevh = n;
for (j = 1; j <= m; j++) {
for (i = 1; i <= prevh; i++) {
if (a[i][j] > mini+x)
break;
}
prevh = i-1;
for (; i <= n; i++) {
if (a[i][j] < maxi-x)
return false;
}
}
return true;
}
bool testAllDiff (int x)
{
return (testDiff(x, a) || testDiff(x, ao) || testDiff(x, av) || testDiff(x, ac));
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
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]);
ao[n-i+1][j] = a[i][j];
av[i][m-j+1] = a[i][j];
ac[n-i+1][m-j+1] = a[i][j];
}
}
st = 0;
dr = maxi-mini;
sol = -1;
while (st <= dr) {
mij = (st+dr) / 2;
bool ok = testAllDiff(mij);
if (ok) {
sol = mij;
dr = mij-1;
}
else {
st = mij+1;
}
}
cout << sol;
return 0;
}
