#include <bits/stdc++.h>
using namespace std;
const int N = 2019;
int H, W;
int A[N][N];
int gmax, gmin;
void flipRow() { for (int i = 0; i < H/2; i++) for (int j = 0; j < W; j++) swap(A[i][j], A[H-i-1][j]); }
void flipCol() { for (int i = 0; i < H; i++) for (int j = 0; j < W/2; j++) swap(A[i][j], A[i][W-j-1]); }
bool check(int t) {
int sp = 0;
for (int i = 0; i < H; i++) {
for (int j = 0; j < W; j++) if (A[i][j] < gmax-t) sp = max(sp,j+1);
for (int j = 0; j < W; j++) if (gmin+t < A[i][j]) if (j < sp) return false;
}
return true;
}
int solve() {
int l = 0, r = gmax-gmin;
while (l < r) {
int mid = (l+r)/2;
if (check(mid)) r = mid;
else l = mid+1;
}
return l;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> H >> W;
for (int i = 0; i < H; i++) for (int j = 0; j < W; j++) cin >> A[i][j];
gmin = gmax = A[0][0];
for (int i = 0; i < H; i++) for (int j = 0; j < W; j++) {
gmin = min(gmin,A[i][j]);
gmax = max(gmax,A[i][j]);
}
int ans = solve();
flipRow();
ans = min(ans,solve());
flipCol();
ans = min(ans,solve());
flipRow();
ans = min(ans,solve());
cout << ans << '\n';
return 0;
}
