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#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const ll MAX = 4e6;
ll dp[MAX];

int main () {
    ios_base::sync_with_stdio(0);
    ll n, k;
    cin >> n >> k;
    dp[0] = 0;
    ll prev = 0;
    ll a = 1;
    ll res = 1e9;
    ll v;
    while (a <= n) {
        for (int i = 0; i < a; ++i) {
            ll id = a * (a + 1) / 2 - a;
            cin >> v;

            ll id2 = (a - 1) * a / 2 - a + 1;
            ll man = 0;
            if (id + i - a < id && id + i - a >= id2) {
                man++;
                dp[id + i] += dp[id + i - a] + 1;
            }
            if (id + i - a + 1 < id && id + i - a + 1 >= id2) {
                man++;
                dp[id + i] += dp[id + i - a + 1] + 1;
            }
            if (man == 2 && id + i - 2 * (a - 1) < id && id + i - 2*(a - 1) >= 0) {
                dp[id + i] -= (dp[id + i - 2*(a - 1)] + 1);
            }
            if (dp[id + i] <= k && v < res) {
                res = v;
            }
        }
        a++;
    }
    cout << res;
}