#include <iostream>
#include <vector>
#include <algorithm>
#include <tuple>
using namespace std;
const int MAX_BOARD_LENGTH = 2000;
const int MAX_VAL = 1e9;
int height, width;
int max_val=-1, min_val=MAX_VAL+7;
int board[MAX_BOARD_LENGTH+7][MAX_BOARD_LENGTH+7];
int tmp[MAX_BOARD_LENGTH+7][MAX_BOARD_LENGTH+7];
void boardRotate90(){
for (int i = 1; i <= height; ++i)
for (int j = 1; j <= width; ++j)
tmp[width-j+1][i] = board[i][j];
swap(height, width);
for (int i = 1; i <= height; ++i)
for (int j = 1; j <= width; ++j)
board[i][j] = tmp[i][j];
}
void boardFlipHorizontal(){
for (int i = 1; i <= height; ++i)
for (int j = 1; j <= width; ++j)
tmp[i][width-j+1] = board[i][j];
for (int i = 1; i <= height; ++i)
for (int j = 1; j <= width; ++j)
board[i][j] = tmp[i][j];
}
bool isAchievable(int k){
if (max_val - min_val <= k) return true;
int curr_max=-1, curr_min=MAX_VAL+7;
int max_height = 0;
for (int j = 1; j <= width; ++j){
int i = height;
while(i > max_height && board[i][j] <= min_val + k) i--;
max_height = i;
while(i > 0){
curr_max = max(curr_max, board[i][j]);
curr_min = min(curr_min, board[i][j]);
--i;
}
}
return (curr_max - curr_min <= k);
}
int getRes(){
int low=0, high=max_val-min_val;
while(low < high){
int mid = (low+high)/2;
if (isAchievable(mid)) high = mid;
else low = mid+1;
}
return high;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> height >> width;
for (int i = 1; i <= height; ++i)
for (int j = 1; j <= width; ++j){
cin >> board[i][j];
max_val = max(max_val, board[i][j]);
min_val = min(min_val, board[i][j]);
}
int res = getRes();
boardRotate90();
res = min(res, getRes());
boardFlipHorizontal();
res = min(res, getRes());
boardRotate90();
res = min(res, getRes());
cout << res << '\n';
return 0;
}
