#include <iostream>

using namespace std;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n, k;

    cin >> n >> k;

    int best;

    cin >> best;

    int **min = new int *[n + 1];

    min[0] = new int[2];
    for (int i = 0; i < 2; ++i) {
        min[0][i] = 0;
    }

    min[1] = new int[3];
    for (int i = 0; i < 3; ++i) {
        min[1][i] = 0;
    }

    int wine;
    for (int row = 2; row <= n; ++row) {
        min[row] = new int[row + 2];
        for (int col = 1; col <= row; ++col) {
            cin >> wine;
            min[row][col] = 1 + min[row - 1][col] + min[row - 1][col - 1] - min[row - 2][col - 1];
            if (wine < best && min[row][col] < k) {
                best = wine;
            }
        }
    }

    cout << best << endl;

    return 0;

}