#include <iostream>
#include <vector>
#include <set>
using namespace std;
vector<vector<int>> values;
vector<vector<int>> parent_count;
int main() {
ios_base::sync_with_stdio(0);
int n,k;
cin >> n >> k;
for (int row=0; row < n; row ++) {
vector<int> r;
vector<int> rpc;
for (int col=0; col < row + 1; col ++) {
int v;
cin >> v;
r.push_back(v);
if (row == 0) {
rpc.push_back(1);
} else {
int pc;
if (row == col)
pc = row;
else
pc = parent_count[row-1][col] + col;
pc++;
rpc.push_back(pc);
//cout << pc << " ";
}
}
//cout << endl;
parent_count.push_back(rpc);
values.push_back(r);
}
int best = 1e9;
pair<int, int> best_pos;
for (int row=0; row < n; row ++) {
for (int col=0; col < row + 1; col ++) {
if (parent_count[row][col] <= k) {
if (values[row][col] < best) {
best = values[row][col];
best_pos = make_pair(row, col);
}
}
}
}
cout << best << endl;
}