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#include <cstdio>
#include <stdio.h>
using namespace std;

int removeNumber(short int row, short int col, int k)
{
    short int col_left = col;
    short int col_right = col;
    int cnt = 1;
    for (short int i = row - 1; i >= 1; i--)
    {
        // if (cnt > k) {
        //      return cnt;
        // }
        col_left -= 1;
        if (col_right > i)
            col_right = i;
        if (col_left == 0)
            col_left = 1;
        cnt += col_right - col_left + 1;
    }
    //printf("\n%hi % hi %d", row, col, cnt);
    return cnt;
}

struct coordinates
{
    short int row;
    short int col;
};

coordinates getCoordinates(short int position)
{
    int cnt = 0;
    struct coordinates coords;
    coords.col = 1, coords.row = 1;
    short int i = 1, j = 1;
    while (coords.row * (coords.row + 1) / 2 < position)
    {
        coords.row++;
    }
    while (coords.row * (coords.row + 1) / 2 - coords.row + coords.col < position)
    {
        coords.col++;
    }
    //printf("coords: %d, %d\n", coords.row, coords.col);
    return coords;
}

int main()
{
    short int n = 0;
    int k = 0;
    scanf("%hi", &n);
    scanf("%d", &k);

    int repeats = n * (n + 1) / 2;

    int firstNumber;
    scanf("%d", &firstNumber);
    if (k == 1)
    {
        printf("%d", firstNumber);
        return 0;
    }

    int cnt = 1;
    short int lowest;
    lowest = firstNumber;
    short int year;

    while (repeats-- > 1)
    {
        scanf("%hi", &year);
        cnt++;
        if (year < lowest)
        {
            coordinates crd = getCoordinates(cnt);
            int result = removeNumber(crd.row, crd.col, k);
            if (result <= k) {
                lowest = year;
            }
        }
    }
    printf("%hi", lowest);
    return 0;
}