#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int N, M;
cin >> N >> M;
vector<vector<int>> A(N, vector<int>(M));
int vmn = INT_MAX, vmx = INT_MIN;
for (int i = 0; i < N; i++) {
for (int j = 0; j < M; j++) {
cin >> A[i][j];
vmn = min(vmn, A[i][j]);
vmx = max(vmx, A[i][j]);
}
}
int ans = INT_MAX;
for (int i = 0; i < 4; i++) {
int bl = 0, br = vmx - vmn;
while (bl < br) {
int bm = (bl + br) / 2;
int bnd = 0, wrk = 1;
for (int i = 0; i < N; i++) {
for (int j = 0; j < M; j++)
if (A[i][j] < vmx - bm)
bnd = max(bnd, j + 1);
for (int j = 0; j < M; j++) {
if (vmn + bm < A[i][j]) {
if (j < bnd) {
wrk = 0;
break;
}
}
}
}
if (wrk)
br = bm;
else
bl = bm + 1;
}
ans = min(ans, bl);
if (i == 0 || i == 2) {
for (int i = 0; i < N / 2; i++)
for (int j = 0; j < M; j++)
swap(A[i][j], A[N - 1 - i][j]);
}
if (i == 1) {
for (int i = 0; i < N; i++)
for (int j = 0; j < M / 2; j++)
swap(A[i][j], A[i][M - 1 - j]);
}
}
cout << ans << '\n';
}
