#include <bits/stdc++.h>
using namespace std;
int numRow, numCol;
#define MAX_N 2020
int a[MAX_N][MAX_N], minCol[MAX_N][MAX_N];
int tmp[MAX_N + 2][MAX_N + 2];
void rotate90() {
swap(numRow, numCol);
for (int i = 1; i <= numRow; ++i)
for (int j = 1; j <= numCol; ++j)
tmp[i][j] = a[j][i];
for (int i = 1; i <= numRow; ++i)
for (int j = 1; j <= numCol; ++j)
a[i][j] = tmp[i][j];
}
void flip180() {
for (int j = 1; j <= numCol; ++j) {
int l = 1, r = numRow;
while (l <= r) swap(a[l++][j], a[r--][j]);
}
}
bool getResults(int rangeAdd) {
int minVal = (int) 1e9 + 7, maxVal = 0;
for (int i = 1; i <= numRow; ++i)
for (int j = 1; j <= numCol; ++j) {
minVal = min(minVal, a[i][j]);
maxVal = max(maxVal, a[i][j]);
}
if (maxVal - minVal <= rangeAdd) return true;
/// min from bot;
for (int j = 1; j <= numCol; ++j) minCol[numRow + 1][j] = 1e9 + 7;
for (int i = numRow; i >= 1; --i) {
for (int j = 1; j <= numCol; ++j) {
minCol[i][j] = min(minCol[i + 1][j], a[i][j]);
}
}
/// inc from left to right;
int last = 1e9, minOther = 1e9 + 7;
for (int j = numCol; j >= 1; --j) {
int high = 0;
for (int i = 1; i <= numRow; ++i) {
if (a[i][j] <= minVal + rangeAdd) {
++high;
} else break;
}
last = min(last, high);
minOther = min(minOther, minCol[last + 1][j]);
}
if (maxVal - minOther <= rangeAdd) return true;
/// inc from right downto left;
last = 1e9, minOther = 1e9 + 7;
for (int j = 1; j <= numCol; ++j) {
int high = 0;
for (int i = 1; i <= numRow; ++i) {
if (a[i][j] <= minVal + rangeAdd) {
++high;
} else break;
}
last = min(last, high);
minOther = min(minOther, minCol[last + 1][j]);
}
if (maxVal - minOther <= rangeAdd) return true;
return false;
}
bool check(int val) {
for (int step = 1; step <= 4; ++step) {
if (step % 2 == 0) flip180();
else rotate90();
if (getResults(val)) return true;
}
return false;
}
int main() {
ios_base::sync_with_stdio(false);cin.tie(nullptr);
cin >> numRow >> numCol;
for (int i = 1; i <= numRow; ++i)
for (int j = 1; j <= numCol; ++j) cin >> a[i][j];
int l = 0, r = (int) 1e9, g, vt = -1;
while (l <= r) {
g = (l + r) >> 1;
if (check(g)) vt = g, r = g - 1;
else l = g + 1;
}
assert(vt != -1);
cout << vt;
return 0;
}
