#include <iostream>
#include <iomanip>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <cassert>
#include <ctime>
#include <chrono>
#include <cstdio>
#include <random>
#include <vector>
#include <string>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <deque>
#include <queue>
#include <bitset>
#include <list>
#include <fstream>
#include <functional>
#include <complex>
using namespace std;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
const long long INF = 1e18, MOD = 1e9 + 7, MOD2 = 998244353, LOG = 18;
const long double EPS = 1e-9, PI = acos(-1);
void solve()
{
long long n, m;
vector<vector<long long>> v;
cin >> n >> m;
v.resize(n, vector<long long>(m));
for (long long i = 0; i < n; i++)
{
for (long long j = 0; j < m; j++)
{
cin >> v[i][j];
}
}
long long mn = INF, mx = -INF;
for (long long i = 0; i < n; i++)
{
for (long long j = 0; j < m; j++)
{
mn = min(mn, v[i][j]);
mx = max(mx, v[i][j]);
}
}
auto build = [&](vector<vector<long long>>& col) -> bool
{
vector<long long> left(n, -1);
for (long long i = 0; i < n; i++)
{
for (long long j = 0; j < m; j++)
{
if (col[i][j] == 0)
{
left[i] = j;
}
}
}
for (long long i = 1; i < n; i++)
{
left[i] = max(left[i], left[i - 1]);
}
bool success = true;
for (long long i = 0; i < n; i++)
{
for (long long j = 0; j < m; j++)
{
if (col[i][j] == 1 && j <= left[i])
{
success = false;
break;
}
}
}
if (success)
{
return true;
}
vector<long long> right(n, m);
for (long long i = 0; i < n; i++)
{
for (long long j = m - 1; j > -1; j--)
{
if (col[i][j] == 0)
{
right[i] = j;
}
}
}
for (long long i = 1; i < n; i++)
{
right[i] = min(right[i], right[i - 1]);
}
success = true;
for (long long i = 0; i < n; i++)
{
for (long long j = 0; j < m; j++)
{
if (col[i][j] == 1 && right[i] <= j)
{
success = false;
break;
}
}
}
if (success)
{
return true;
}
return false;
};
auto check = [&](long long mid) -> bool
{
vector<vector<long long>> col(n, vector<long long>(m, -1));
long long l0 = mn, r0 = mn + mid, l1 = mx - mid, r1 = mx;
for (long long i = 0; i < n; i++)
{
for (long long j = 0; j < m; j++)
{
if (l1 <= v[i][j] && v[i][j] <= r0)
{
continue;
}
if (l0 <= v[i][j] && v[i][j] <= r0)
{
col[i][j] = 0;
}
else if (l1 <= v[i][j] && v[i][j] <= r1)
{
col[i][j] = 1;
}
else
{
return false;
}
}
}
if (build(col))
{
return true;
}
for (long long i = 0; i < n; i++)
{
for (long long j = 0; j < m; j++)
{
if (col[i][j] == -1)
{
continue;
}
col[i][j] ^= 1;
}
}
if (build(col))
{
return true;
}
return false;
};
long long left = -1, right = mx - mn;
while (right - left > 1)
{
long long mid = (left + right) / 2;
if (check(mid))
{
right = mid;
}
else
{
left = mid;
}
}
cout << right << "\n";
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
srand(time(NULL));
int tst = 1;
//cin >> tst;
while (tst--)
{
solve();
}
return 0;
}
/*
<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3
⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⠤⠖⠚⢉⣩⣭⡭⠛⠓⠲⠦⣄⡀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⢀⡴⠋⠁⠀⠀⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠳⢦⡀⠀⠀⠀⠀
⠀⠀⠀⠀⢀⡴⠃⢀⡴⢳⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⣆⠀⠀⠀
⠀⠀⠀⠀⡾⠁⣠⠋⠀⠈⢧⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢧⠀⠀
⠀⠀⠀⣸⠁⢰⠃⠀⠀⠀⠈⢣⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⣇⠀
⠀⠀⠀⡇⠀⡾⡀⠀⠀⠀⠀⣀⣹⣆⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢹⠀
⠀⠀⢸⠃⢀⣇⡈⠀⠀⠀⠀⠀⠀⢀⡑⢄⡀⢀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇
⠀⠀⢸⠀⢻⡟⡻⢶⡆⠀⠀⠀⠀⡼⠟⡳⢿⣦⡑⢄⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇
⠀⠀⣸⠀⢸⠃⡇⢀⠇⠀⠀⠀⠀⠀⡼⠀⠀⠈⣿⡗⠂⠀⠀⠀⠀⠀⠀⠀⢸⠁
⠀⠀⡏⠀⣼⠀⢳⠊⠀⠀⠀⠀⠀⠀⠱⣀⣀⠔⣸⠁⠀⠀⠀⠀⠀⠀⠀⢠⡟⠀
⠀⠀⡇⢀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠠⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⢸⠃⠀
⠀⢸⠃⠘⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⠁⠀⠀⢀⠀⠀⠀⠀⠀⣾⠀⠀
⠀⣸⠀⠀⠹⡄⠀⠀⠈⠁⠀⠀⠀⠀⠀⠀⠀⡞⠀⠀⠀⠸⠀⠀⠀⠀⠀⡇⠀⠀
⠀⡏⠀⠀⠀⠙⣆⠀⠀⠀⠀⠀⠀⠀⢀⣠⢶⡇⠀⠀⢰⡀⠀⠀⠀⠀⠀⡇⠀⠀
⢰⠇⡄⠀⠀⠀⡿⢣⣀⣀⣀⡤⠴⡞⠉⠀⢸⠀⠀⠀⣿⡇⠀⠀⠀⠀⠀⣧⠀⠀
⣸⠀⡇⠀⠀⠀⠀⠀⠀⠉⠀⠀⠀⢹⠀⠀⢸⠀⠀⢀⣿⠇⠀⠀⠀⠁⠀⢸⠀⠀
⣿⠀⡇⠀⠀⠀⠀⠀⢀⡤⠤⠶⠶⠾⠤⠄⢸⠀⡀⠸⣿⣀⠀⠀⠀⠀⠀⠈⣇⠀
⡇⠀⡇⠀⠀⡀⠀⡴⠋⠀⠀⠀⠀⠀⠀⠀⠸⡌⣵⡀⢳⡇⠀⠀⠀⠀⠀⠀⢹⡀
⡇⠀⠇⠀⠀⡇⡸⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⠮⢧⣀⣻⢂⠀⠀⠀⠀⠀⠀⢧
⣇⠀⢠⠀⠀⢳⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⡎⣆⠀⠀⠀⠀⠀⠘
⢻⠀⠈⠰⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠰⠘⢮⣧⡀⠀⠀⠀⠀
⠸⡆⠀⠀⠇⣾⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⠆⠀⠀⠀⠀⠀⠀⠀⠙⠳⣄⡀⢢⡀
<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3
*/
