#include<bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 2e3 + 5;
const int INF = 1e11;
int a[MAXN][MAXN];
int n, m;
int maxx = -1;
int b[MAXN][MAXN];
void xoay()
{
for (int i = 1; i <= m; i++)
{
for (int j = 1; j <= n; j++)
{
b[i][j] = a[n - j + 1][i];
}
}
swap(n, m);
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
{
a[i][j] = b[i][j];
}
}
}
bool ck(int mid)
{
int pos = INF;
int mx = -INF;
int mn = INF;
for (int i = 1; i <= n; i++)
{
int cur = 0;
while(cur < m and a[i][cur + 1] >= maxx - mid) cur++;
pos = min(pos, cur);
for (int j = pos + 1; j <= m; j++)
{
mx = max(mx, a[i][j]);
mn = min(mn, a[i][j]);
}
}
return (mx == -INF || mx - mn <= mid);
}
bool peal(int mid)
{
bool cak1 = ck(mid);
xoay();
bool cak2 = ck(mid);
xoay();
bool cak3 = ck(mid);
xoay();
bool cak4 = ck(mid);
xoay();
if (cak1 == true || cak2 == true || cak3 == true || cak4 == true)
{
return true;
}
return false;
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
{
cin >> a[i][j];
maxx = max(maxx, a[i][j]);
}
}
int l = 0;
int r = 1e9;
int ans = -1;
while(l <= r)
{
int mid = (l + r) / 2;
if (peal(mid))
{
ans = mid;
r = mid - 1;
}
else
{
l = mid + 1;
}
}
cout << ans;
}
