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//Krzysztof Boryczka
#pragma GCC optimize "O3"
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
const int inf=0x3f3f3f3f;
const ll INF=0x3f3f3f3f3f3f3f3f;

#define FOR(i, b, e) for(int i=b; i<=e; i++)
#define FORD(i, b, e) for(int i=b; i>=e; i--)
#define SIZE(x) ((int)x.size())
#define pb push_back
#define st first
#define nd second
#define sp ' '
#define ent '\n'

int n, k, a, ans;

void solve(){
	ans=inf;
	cin>>n>>k;
	FOR(i, 1, n) FOR(j, 1, i){
		cin>>a;
		if(j*(i-j+1)<=k) ans=min(ans, a);
	}
	cout<<ans<<ent;
}

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	// int tt; cin>>tt;
	// FOR(te, 1, tt)
	solve();
	return 0;
}