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#include<bits/stdc++.h>
#define VAR(i,n) __typeof(n) i = (n)
#define loop(i,j,s) for(int i=j;i<s;i++)
#define loopback(i,j,s) for(int i=j;i>=s;i--)
#define foreach(i,c) for(VAR(i,(c).begin());i!=(c).end();i++)
#define pln( x ) cout << x << "\n"
#define ps( x ) cout << x << " "
#define entr cout << "\n"
#define pcnt(i) __builtin_popcount(i)
#define ll long long
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define SIZE(c) (c).size()
#define ALL(c) (c).begin(), (c).end()
using namespace std;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef vector<vector<int> > VVI;
const int INFTY=20000000;
const int MAX=500100;
const int MOD=10000000;

void coutTab(int* tab,int n){
	loop(i,0,n){
		cout<<tab[i]<<" ";
	}
	cout<<"\n";
}

template<class T> void coutVec(vector<T> tab){
	for(T t : tab){
		cout<<t<<" ";
	}
	cout<<"\n";
}
//------------------------------------------
int main(){
	ios_base::sync_with_stdio(0);
	int n,k;
	cin>>n>>k;
	int a;
	int best=2020;
	int N = (n-1)*n/2;
	loop(i,1,n+1) {
		loop(j,0,i) {
			cin>>a;
			int l = N - (N - (i+1)*i/2 + j*(j+1)/2 + (i-j-1)*(i-j)/2);
			if(l <= k){
				best = min(best, a);
			}
		}
	}
	pln(best);
}