#include <vector>
#include <cstdio>
#include <iostream>
using namespace std;
int bottles(int y, int x) {
return (x + 1) * (y - x);
}
int main() {
int n, k;
scanf("%d%d", &n, &k);
vector<vector<int>> pyramid(n + 1);
for (int i = 1; i <= n; i++) {
for (int j = 0; j < i; j++) {
int year;
scanf("%d", &year);
pyramid[i].push_back(year);
}
}
int out = 2020;
for (int i = 1; i <= n; i++) {
for (int j = 0; j < i; j++) {
//cerr << i << " " << j << " " <<bottles(i, j) << "\n";
if (pyramid[i][j] < out && bottles(i, j) <= k)
out = pyramid[i][j];
}
}
printf("%d", out);
return 0;
}