#include<bits/stdc++.h>
using namespace std;
#define st first
#define nd second
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
#define boost ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
typedef long long lli;
typedef pair<int, int> pii;
typedef pair<lli, lli> pll;
typedef pair<lli, int> pli;
typedef pair<int, lli> pil;
const int N = 2137;
int n, k, a, wyn = N;
int32_t main()
{
boost;
cin >> n >> k;
for(int i = 1; i <= n; ++i){
for(int j = 1; j <= i; ++j){
cin >> a;
if(j * (i - j + 1) <= k)wyn = min(wyn, a);
}
}
cout << wyn << "\n";
return 0;
}