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;
enum mod = 1_000_000_007L;


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

    long ng = -infl, ok = infl;

    bool check(long mid) {
        long cnt;
        foreach (i ; 0 .. N) {
            if (A[i] > 0) {
                auto d = mid / A[i];
                if (mid < 0 && mid % A[i] != 0) d--;
                cnt += A[i + 1 .. $].lowerBound(d + 1).length;
            }
            else if (A[i] < 0) {
                auto d = mid / A[i];
                if (mid < 0 && mid % A[i] != 0) d++;
                cnt += A[i + 1 .. $].upperBound(d - 1).length;
            }
            else { // A[i] == 0
                cnt += mid >= 0 ? N - 1 - i : 0;
            }
        }
        debug {
            writefln("%s: %s", mid, cnt);
        }
        return cnt >= K;
    }

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

    writeln(ok);
}



void scan(T...)(ref T args) {
    import std.stdio : readln;
    import std.algorithm : splitter;
    import std.conv : to;
    import std.range.primitives;

    auto line = readln().splitter();
    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;
}
