#include <bits/stdc++.h>
using namespace std;
vector<vector<int>> grid;
void reverse_rows(){
for(auto &i : grid){
reverse(i.begin(), i.end());
}
}
void reverse_cols(){
reverse(grid.begin(), grid.end());
}
int good(int mini, int K){
int H = grid.size();
int W = grid[0].size();
int can_go = W;
int mind = 1e9, maxd = 0;
for(int i = 0; i < H; i ++){
for(int j = 0; j < can_go; j ++){
if(mini + K < grid[i][j])can_go = j;
}
for(int j = can_go; j < W; j ++){
maxd = max(grid[i][j], maxd);
mind = min(grid[i][j], mind);
}
}
return maxd-mind;
}
int check(int K, int mini){
int pass = 0;
reverse_rows();
pass |= (good(mini, K) <= K);
reverse_cols();
pass |= (good(mini, K) <= K);
reverse_rows();
pass |= (good(mini, K) <= K);
reverse_cols();
pass |= (good(mini, K) <= K);
return pass;
}
int main(){
int H, W;
cin >> H >> W;
int mini = 1e9;
grid.assign(H, vector<int>(W));
for(int i = 0; i < H; i ++){
for(int j = 0; j < W; j ++){
cin >> grid[i][j];
mini = min(grid[i][j], mini);
}
}
int L = 0, R = 1e9;
while(L < R){
int mid = (L + R) / 2;
int t = check(mid, mini);
if(t){
R = mid;
}
else{
L = mid + 1;
}
}
cout << L << endl;
return 0;
}
