#include<iostream>
#include<assert.h>
#include<cstdio>
#include<string>
#include<cmath>
#include<bitset>
#include<vector>
#include<map>
#include<set>
#include<algorithm>
#include<utility>
using namespace std;
std::vector<int> FillRow(int row_nr) {
std::vector<int> row;
int needed = row_nr;
int v = row_nr - 1;
for (int i = 0; i < (row_nr + 2) / 2; i++) {
row.push_back(needed);
needed += v;
v -= 2;
}
return row;
}
int SolveTestCase() {
int n, k;
std::cin >> n >> k;
int result = 2019;
for (int row = 0; row < n; row++) {
auto needed = FillRow(row);
for (int col = 0; col <= row; ++col) {
int age;
std::cin >> age;
if (needed[std::min(col, row - col)] < k) {
result = std::min(result, age);
}
}
}
return result;
}
int main() {
std::ios::sync_with_stdio(false);
std::cout << SolveTestCase() << '\n';
return 0;
}