import std.stdio, std.string, std.conv, std.range;
import std.algorithm, std.array, std.typecons, std.container;
import std.math, std.numeric, std.random, core.bitop;

enum inf = 1_001_001_001;
enum infl = 1_001_001_001_001_001_001L;


void main() {
    int N; long K;
    scan(N, K);
    auto a = readln.split.to!(long[]);

    long[] pos, neg;
    long zero;

    foreach (ai ; a) {
        if (ai > 0) {
            pos ~= ai;
        }
        else if (ai < 0) {
            neg ~= ai;
        }
        else {
            zero++;
        }
    }

    pos.sort();
    neg.sort!"a > b"();

    int Ps = pos.length.to!int;
    int Ng = neg.length.to!int;

    bool check(long x) {
        long cnt;

        if (x >= 0) {
            cnt += zero * (zero - 1) / 2;
            cnt += zero * (N - zero);
            cnt += 1L * Ps * Ng;

            int r = Ps - 1;
            foreach (i ; 0 .. Ps) {
                while (r >= 0 && pos[r] * pos[i] > x) r--;
                cnt += max(r - i, 0);
            }

            r = Ng - 1;
            foreach (i ; 0 .. Ng) {
                while (r >= 0 && neg[r] * neg[i] > x) r--;
                cnt += max(r - i, 0);
            }
        }
        else {
            int r = Ng - 1;
            foreach (i ; 0 .. Ps) {
                while (r >= 0 && pos[i] * neg[r] <= x) r--;
                cnt += Ng - 1 - r;
            }
        }

        debug {
            writefln("x :%s, cnt: %s", x, cnt);
        }

        return cnt >= K;
    }

    long ng = -infl, ok = infl;
    while (abs(ok - ng) > 1) {
        auto mid = (ok + ng) / 2;
        (check(mid) ? ok : ng) = mid;
    }

    writeln(ok);
}



void scan(T...)(ref T args) {
    auto line = readln.split;
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront;
    }
    assert(line.empty);
}

void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}

bool chmin(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args) if (x > arg) {
        x = arg;
        isChanged = true;
    }
    return isChanged;
}

bool chmax(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args) if (x < arg) {
        x = arg;
        isChanged = true;
    }
    return isChanged;
}

void yes(bool ok, string y = "Yes", string n = "No") {
    return writeln(ok ? y : n);
}
