#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define pb push_back
#define F first
#define S second
#define in insert
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N = 1e6 + 123;
const int P = 320;
const int mod = 1e9 + 7;
ll n, m, k;
ll a[N];
ll t[N * 4];
ll dp[1005][1005];
vector <ll> v;
void salemkhan() {
cin >> n >> m;
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= m; j++) {
cin >> a[j];
v.pb(a[j]);
}
}
ll ans = mod;
for(int i = 1; i <= m; i++) {
for(int j = i + 1; j <= m; j++) {
ll cur1 = *max_element(v.begin() + i - 1, v.begin() + j - 1);
ll cur2 = *min_element(v.begin() + i - 1, v.begin() + j - 1);
ans = min(ans, (cur1 - cur2) - (j - i + 1));
}
}
cout << ans << '\n';
}
// 28 37 48 49 55 56 57 58 67 9
// 9 + 1 +
int main() {
//freopen("knight.in", "r", stdin);
//freopen("knight.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll tt = 1;
//cin >> tt;
while(tt--) {
salemkhan();
}
}
