#include <iostream>

using namespace std;

int tab [2009][6009];
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n, k;
    cin >>n >>k;

    int m = 2020;
    tab[0][2999] = -1;
    
    for (int i = 1; i <= n; i++)
    {
        for (int j = 3001-i; j <= 2999+i; j+=2)
        {
                int x; cin >>x;
                
                tab[i][j] = tab[i-1][j-1] + tab[i-1][j+1] + 1;
                if ( tab[i][j] <= k && x < m) m = x;
        }
    }

    cout <<m;

    return 0;
}