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#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <sstream>
#include <set>
#include <map>
#include <vector>
#include <list>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <string>
#include <queue>
#include <bitset>		//UWAGA - w czasie kompilacji musi byc znany rozmiar wektora - nie mozna go zmienic
#include <cassert>
#include <iomanip>		//do setprecision
#include <ctime>
#include <complex>
#include <chrono>
#include<unordered_map>
using namespace std;

#define FOR(i,b,e) for(int i=(b);i<(e);++i)
#define FORQ(i,b,e) for(int i=(b);i<=(e);++i)
#define FORD(i,b,e) for(int i=(b)-1;i>=(e);--i)
#define REP(x, n) for(int x = 0; x < (n); ++x)
#define ALL(u) (u).begin(),(u).end()

#define ST first
#define ND second
#define PB push_back
#define MP make_pair
#define LL long long
#define ULL unsigned LL
#define LD long double

typedef pair<int, int> PII;

const double pi = 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342;

const int MR = 2030;

int ile[MR][MR];

int main()
{
	int n, k;
	scanf("%d%d", &n, &k);
	int res = MR;

	REP(i, n)REP(j, i + 1)
	{
		int v;
		scanf("%d", &v);

		if (i)
		{
			if (!j)
				ile[i][j] = ile[i - 1][j] + 1;
			else if (j < i)
				ile[i][j] = ile[i - 1][j - 1] + ile[i - 1][j] - ile[i - 2][j - 1] + 1;
			else
				ile[i][j] = ile[i - 1][j - 1] + 1;
		}
		else
			ile[i][j] = 1;

		if (ile[i][j] <= k)
			res = min(res, v);
	}

	printf("%d\n", res);

	return 0;
}

// FOR GNU C++ use the following pattern:
// Uncomment the code below and change your main into main2
// It does not build in MS C++
// But it does increase the stack size from 256 MB on CF and uses GNU C++

//#include <Processthreadsapi.h>
//#include <iostream>
//#include <Synchapi.h>
//#include <windows.h>
//#include <process.h>
//
//DWORD WINAPI MyThreadFunction(LPVOID lpParam) {
//    main2(nullptr);
//    return 0;
//}
//int main() {
//    auto h = CreateThread(nullptr, 1024 << 20, MyThreadFunction, nullptr, STACK_SIZE_PARAM_IS_A_RESERVATION, nullptr);
//    WaitForSingleObject(h, INFINITE);
//}