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[]).sort();

    bool check(long x) {
        long cnt;

        foreach (i ; 0 .. N) {
            if (a[i] > 0) {
                auto y = x / a[i];
                if (x < 0 && x % a[i] != 0) y--;
                auto j = a[i + 1 .. $].lowerBound(y + 1).length.to!int;
                cnt += j;
            }
            else if (a[i] < 0) {
                auto y = x / a[i];
                if (x < 0 && x % a[i] != 0) y++;
                auto j = a[i + 1 .. $].upperBound(y - 1).length.to!int;
                cnt += j;
            }
            else {
                assert(a[i] == 0);
                cnt += x >= 0 ? N - 1 - i : 0;
            }
        }

        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);
}
