import java.util.Arrays;
import java.io.PrintWriter;
import java.io.FileNotFoundException;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.IOException;
import java.util.InputMismatchException;
import java.util.TreeMap;

public class Main {
    InputStream is;

    int __t__ = 1;
    int __f__ = 0;
    int __FILE_DEBUG_FLAG__ = __f__;
    String __DEBUG_FILE_NAME__ = "src/D4";

    FastScanner in;
    PrintWriter out;

    public void solve() {
        int n = in.nextInt();
        long k = in.nextLong();
        long[] a = in.nextLongArray(n);
        int plusCnt = 0;
        for (int i = 0; i < n; i++) {
            if (a[i] > 0) plusCnt++;
        }
        int minusCnt = n - plusCnt;
        long[] plus = new long[plusCnt];
        long[] minus = new long[minusCnt];
        for (int i = 0, pp = 0, mp = 0; i < n; i++) {
            if (a[i] > 0) {
                plus[pp++] = a[i];
            } else {
                minus[mp++] = -a[i];
            }
        }
        Arrays.sort(plus);
        Arrays.sort(minus);
        long[] minus2 = new long[minusCnt];
        for (int i = 0; i < minusCnt; i++) {
            minus2[i] = minus[minusCnt-i-1];
        }

        long lo = (long) -(1e18 + 10), hi = (long) (1e18 + 10);
        while (hi - lo > 1) {
            long mid = (lo + hi) / 2;
            long x = calc(plus, minus, minus2, mid);
            if (x < k) {
                lo = mid;
            } else {
                hi = mid;
            }
        }
        System.out.println(hi);
    }

    private long calc(long[] plus, long[] minus, long[] minus2, long target) {
        long res = 0;
        res += calc2(plus, target);
        res += calc2(minus, target);
        /*
        for (long p : plus) {
            for (long m : minus) {
                if (-(p * m) <= target) {
                    res++;
                }
            }
        }
         */
        for (long p : plus) {
            int lo = -1, hi = minus2.length;
            while (hi - lo > 1) {
                int mid = (lo + hi) / 2;
                if (-(p * minus2[mid]) <= target) {
                    lo = mid;
                } else {
                    hi = mid;
                }
            }
            res += lo + 1;
        }
        return res;
    }

    private long calc2(long[] a, long target) {
        long res = 0;
        for (int i = 1; i < a.length; i++) {
            int lo = -1, hi = i;
            while (hi - lo > 1) {
                int mid = (lo + hi) / 2;
                if (a[i] * a[mid] <= target) {
                    lo = mid;
                } else {
                    hi = mid;
                }
            }
            res += lo + 1;
        }
        return res;
    }


    public void run() {
        if (__FILE_DEBUG_FLAG__ == __t__) {
            try {
                is = new FileInputStream(__DEBUG_FILE_NAME__);
            } catch (FileNotFoundException e) {
                // TODO 自動生成された catch ブロック
                e.printStackTrace();
            }
            System.out.println("FILE_INPUT!");
        } else {
            is = System.in;
        }
        in = new FastScanner(is);
        out = new PrintWriter(System.out);

        solve();
    }

    public static void main(final String[] args) {
        new Main().run();
    }

}


class FastScanner {
    private InputStream stream;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;

    public FastScanner(InputStream stream) {
        this.stream = stream;
        // stream = new FileInputStream(new File("dec.in"));
    }

    int read() {
        if (numChars == -1)
            throw new InputMismatchException();
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = stream.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0)
                return -1;
        }
        return buf[curChar++];
    }

    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    public boolean isEndline(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

    public int[] nextIntArray(int n) {
        int[] array = new int[n];
        for (int i = 0; i < n; i++)
            array[i] = nextInt();

        return array;
    }

    public int[][] nextIntMap(int n, int m) {
        int[][] map = new int[n][m];
        for (int i = 0; i < n; i++) {
            map[i] = nextIntArray(m);
        }
        return map;
    }

    public long nextLong() {
        return Long.parseLong(next());
    }

    public long[] nextLongArray(int n) {
        long[] array = new long[n];
        for (int i = 0; i < n; i++)
            array[i] = nextLong();

        return array;
    }

    public long[][] nextLongMap(int n, int m) {
        long[][] map = new long[n][m];
        for (int i = 0; i < n; i++) {
            map[i] = nextLongArray(m);
        }
        return map;
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }

    public double[] nextDoubleArray(int n) {
        double[] array = new double[n];
        for (int i = 0; i < n; i++)
            array[i] = nextDouble();

        return array;
    }

    public double[][] nextDoubleMap(int n, int m) {
        double[][] map = new double[n][m];
        for (int i = 0; i < n; i++) {
            map[i] = nextDoubleArray(m);
        }
        return map;
    }

    public String next() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }

    public String[] nextStringArray(int n) {
        String[] array = new String[n];
        for (int i = 0; i < n; i++)
            array[i] = next();

        return array;
    }

    public String nextLine() {
        int c = read();
        while (isEndline(c))
            c = read();
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndline(c));
        return res.toString();
    }

    public int[][] nextPackedIntArrays(int packN, int size) {
        int[][] res = new int[packN][size];
        for (int i = 0; i < size; i++) {
            for (int j = 0; j < packN; j++) {
                res[j][i] = nextInt();
            }
        }
        return res;
    }
}


Measured memory_bytes: 45080