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#include <bits/stdc++.h>
using namespace std;

typedef long long LL;
typedef long double LD;
typedef pair < int, int > PII;
typedef pair < LL, LL > PLL;
typedef pair < LD, LD > PDD;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define dbl(k, x) fixed << setprecision(k) << (x)

template < typename _T > inline void _DBG(const char *s, _T x) { cerr << s << " = " << x << "\n"; }
template < typename _T, typename... args > void _DBG(const char *s, _T x, args... a) { while(*s != ',') cerr << *s++; cerr << " = " << x << ','; _DBG(s + 1, a...); }

#ifdef LOCAL
#define _upgrade ios_base::sync_with_stdio(0);
#define DBG(...) _DBG(#__VA_ARGS__, __VA_ARGS__)
#else
#define _upgrade ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define DBG(...) (__VA_ARGS__)
#define cerr if(0) cout
#endif

// ********************** CODE ********************** //

const int N = 2007;
const int INF = 1e9;

int n, k, T[N][N], cnt[N][N], col[N][N];

int main()
{
    _upgrade
    
    cin >> n >> k;
    
    int ans = INF;

    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= i; j++)
        {
            cin >> T[i][j];
            col[i][j] = col[i - 1][j] + 1;
            cnt[i][j] = cnt[i - 1][j - 1] + col[i][j];
            if(cnt[i][j] <= k)
                ans = min(ans, T[i][j]);
        }
    }
    
    cout << ans << "\n";
    
	return 0;
}