#include <bits/stdc++.h>
#include <queue>
#include <iostream>
using namespace std;
#define int long long
typedef pair<int, int> pi;
signed main(){
int n, s;
cin >> n >> s;
vector<int> sch[1005];
int counter[1005];
memset(counter, 0, sizeof(counter));
pi bottom = make_pair(-1, -1);
priority_queue<pi> pq;
for(int i = 0; i < n; i++){
cout << i << endl;
vector<int> temp;
for(int j = 0; j < s; j++){
int x;
cin >> x;
temp.push_back(x);
}
sort(temp.begin(), temp.end(), greater<int>());
sch[i] = temp;
if(bottom.first == -1 or temp[0] < bottom.first){
bottom = make_pair(temp[0], i);
}
pq.push(make_pair(temp[s-1], i));
}
int ans = pq.top().first - bottom.first;
while(!pq.empty()){
pi curr = pq.top();
pq.pop();
ans = min(curr.first - bottom.first, ans); //max - min
if(counter[curr.second] == s-1) break;
else {
counter[curr.second]++;
pq.push(make_pair(counter[curr.second], curr.second));
if(sch[curr.second][counter[curr.second]] < bottom.first){
bottom = make_pair(sch[curr.second][counter[curr.second]], curr.second);
}
}
}
cout << ans << '\n';
}
