#include <bits/stdc++.h>
#define FOR(x, a, b) for (int x = a; x <= b; ++x)
#define FOD(x, a, b) for (int x = a; x >= b; --x)
#define REP(x, a, b) for (int x = a; x < b; ++x)
#define DEBUG(X) { cout << #X << " = " << X << endl; }
#define PR(A, n) { cout << #A << " = "; FOR(_, 1, n) cout << A[_] << " "; cout << endl; }
#define PR0(A, n) { cout << #A << " = "; REP(_, 0, n) cout << A[_] << " "; cout << endl; }
using namespace std;
typedef long long LL;
const int N = 2e3 + 10;
const int INF = 0x3f3f3f3f;
int n, m, minV = INF, maxV = -INF, nn, mm;
int a[N][N], b[4][N][N], NN[4], MM[4];
void Rotate(int x, int y) {
int nn = NN[x], mm = MM[x];
FOR(i, 1, nn)
FOR(j, 1, mm) b[y][j][i] = b[x][nn - i + 1][j];
NN[y] = mm; MM[y] = nn;
}
void Init() {
NN[0] = n; MM[0] = m;
FOR(i, 1, NN[0])
FOR(j, 1, MM[0]) b[0][i][j] = a[i][j];
Rotate(0, 1);
Rotate(1, 2);
Rotate(2, 3);
}
bool Greedy(int t, int diff) {
nn = NN[t], mm = MM[t];
int l = minV, r = l + diff;
vector <int> f;
int p = mm;
FOR(i, 1, nn) {
FOR(j, 1, p) {
if (l <= b[t][i][j] && b[t][i][j] <= r) continue;
p = j - 1;
break;
}
f.push_back(p);
}
int x = INF, y = -INF;
FOR(i, 1, nn) {
int p = f[i - 1];
FOR(j, p + 1, mm) {
x = min(x, b[t][i][j]);
y = max(y, b[t][i][j]);
}
}
if (x == INF) return true;
else return abs(x - y) <= diff;
}
bool Check(int diff) {
if (Greedy(0, diff) == true) return true;
if (Greedy(1, diff) == true) return true;
if (Greedy(2, diff) == true) return true;
if (Greedy(3, diff) == true) return true;
return false;
}
int main() {
// freopen("KUTO.INP", "r", stdin);
// freopen("KUTO.OUT", "w", stdout);
scanf("%d%d", &n, &m);
FOR(i, 1, n)
FOR(j, 1, m) scanf("%d", &a[i][j]);
FOR(i, 1, n)
FOR(j, 1, m) {
minV = min(minV, a[i][j]);
maxV = max(maxV, a[i][j]);
}
Init();
int l = 0, r = maxV - minV, f = -1;
while (l <= r) {
int m = (l + r) >> 1;
if (Check(m)) {
r = m - 1;
f = m;
} else l = m + 1;
}
printf("%d", f);
return 0;
}
