#include <iostream>
using namespace std;
int main () {
int n = 0, k = 0;
cin >> n; cin >> k;
int ii = n;
short tower[n+1][n+1];
if (k < n) {
ii = k;
}
for (int i = 1; i <= ii; i++) {
for (int j = 1; j <= i; j++) {
cin >> tower[i][j];
}
}
short kingsWine = 3000;
for (int i = 1; i <= ii; i++) {
if (( i / 2 + 1 ) * ( i - i / 2 ) <= k) {
for (int j = 1; j <= i; j++) {
if (tower[i][j] < kingsWine) {
kingsWine = tower[i][j];
}
}
} else {
for (int j = 1; j <= i; j++) {
if (j * ( i - j + 1 ) <= k && tower[i][j] < kingsWine) {
kingsWine = tower[i][j];
}
}
}
}
cout << kingsWine;
return 0;
}