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// Author: Kamil Nizinski
// NOLINT(legal/copyright)
#ifdef LOCAL
#ifdef COLOR
#include "bits/cp_local_color.h"
#else
#include "bits/cp_local.h"
#endif
#else
#include "bits/stdc++.h"
#define debug_arr(arr_name, first, last)
#define debug(...)
#define cerr if (false) cerr
#define speed_of_cin_and_cout ios_base::sync_with_stdio(0), cin.tie(0)
#define local if (false)
#endif
#define ft first
#define sd second
#define psb push_back
#define sz(a) (static_cast<int>((a).size()))
using namespace std;  // NOLINT(build/namespaces)
typedef int64_t LL;
typedef uint64_t LLU;
typedef long double LD;
typedef pair<int, int> PII;
const int kInf = 1000000007;
int solve() {
  int n, k;
  cin >> n >> k;
  int answer = kInf;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= i; j++) {
      int a;
      cin >> a;
      if (j * (i - j + 1) <= k)
        answer = min(answer, a);
    }
  }
  return answer;
}

int main() {
  speed_of_cin_and_cout;
  int test_cases_num = 1;
//   cin >> test_cases_num;
  for (int i = 1; i <= test_cases_num; i++) {
    local if (test_cases_num > 1) cerr << "Test #" << i << ":\n";
    cout << solve() << "\n";
    local if (test_cases_num > 1) cerr << "End of test #" << i << ".\n";
  }
  return 0;
}