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#include <cstdio>

using namespace std;

int min(int a, int b) {
    return a < b ? a : b;
}

int main() {
    int n, k, s;
    scanf("%d%d", &n, &k);
    s = n * (n + 1) / 2;

    int a, c = 1, l = 1, m = 2020;
    for (int i = 0; i < s; i++) {
        scanf("%d", &a);
        if ((l + 1 - c) * c <= k) {
            m = min(m, a);
        }

        if (c == l) {
            l++;
            c = 1;
        } else {
            c += 1;
        }
    }
    printf("%d\n", m);
    return 0;
}