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#include <stdio.h>
#include <time.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <map> 
#include <string>
#include <vector>  
#include <iostream> 
#include <sstream> 
#include <queue>
#include <algorithm>
#include <assert.h>


using namespace std;

#define ll long long
#define PB 		push_back
#define FOR(a,start,end) 	for(int a=int(start); a<int(end); a++)
#define INF 		INT_MAX
#define SORT(a) 	sort(a.begin(),a.end()) 
#define CL(a,x) 		memset(a,x,sizeof(a))
#define REP(a,x)	for(int a=0;a<x;a++)
#define REP1(a,x)	for(int a=1;a<=x;a++)
#define MP 		make_pair



typedef vector<ll>     vi;
typedef pair<ll, ll>     pii;
typedef vector<string> vs;
typedef vector<pii> vii;
typedef vector<vector<ll> > vvi;
typedef vector<vector<string> > vvs;
typedef vector<pair<string, string> > vss;
typedef pair<string, string> pss;
typedef pair<ll, pii> ppii;
typedef vector<ppii> vppii;
typedef vector<vector<pii> > vvii;
typedef vector<vvi> vvvi;


ll n, k, a, b, c, i, j, q, t,z;
vi vk, va, vb;
vvi vvk;

int main() {
	//	freopen( "c:\\wojtek\\uva\\pa\\debug\\1.in", "rt", stdin);  

		//pi=2*acos(0.0);
	scanf("%lld%lld", &n, &k);
	//cin >> n>>k;
	vvk.clear();
	z = 2019;
	for (int i = 0; i < n; i++) {
		vk.clear();
		for (int j = 0; j < i + 1; j++) {
			scanf("%lld", &a);
			//cin >> a;
			vk.push_back(a);
		}
		vvk.push_back(vk);

	}
	c = min(k, n)-1;

	for (; c >= 0; c--) {
		b = 1;
		a = c;
		while (((a + 1)*b <= k) && ((b-1) <= (c / 2))) {
			z = min(z, vvk[c][b - 1]);
			z = min(z, vvk[c][c-(b - 1)]);
			a--;
			b++;
		}
		

	}


	printf("%lld\n", z);
	//cout << z << endl;


	
	return 0;

}