#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
#define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
using namespace std;
using ll = long long;
// template end
void solve() {
int n, m;
cin >> n >> m;
vector<int> a[n + 5], ptr(n + 5, 0);
priority_queue<pair<int, int>> pq;
int mx = -1;
int ans = 1e9 + 7;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
int dt;
cin >> dt;
a[i].push_back(dt);
}
sort(a[i].begin(), a[i].end());
pq.push({-a[i][0], i});
mx = max(mx, a[i][0]);
}
while (!pq.empty()) {
int mn = -pq.top().first;
int idx = pq.top().second;
pq.pop();
ans = min(ans, mx - mn);
ptr[idx]++;
if (ptr[idx] >= m) {
break;
}
mx = max(mx, a[idx][ptr[idx]]);
pq.push({-a[idx][ptr[idx]], idx});
}
cout << ans << "\n";
}
int main(void) {
fastio;
int t = 1;
// cin >> t;
while (t--) {
solve();
}
return 0;
}
