#include <bits/stdc++.h>
using namespace std;

using i64 = int64_t;

#define rep(i, x, y) for (i64 i = i64(x), i##_max_for_repmacro = i64(y); i < i##_max_for_repmacro; ++i)
#define debug(x) #x << "=" << (x)

#ifdef DEBUG
#define _GLIBCXX_DEBUG
#define print(x) std::cerr << debug(x) << " (L:" << __LINE__ << ")" << std::endl
#else
#define print(x)
#endif

template <i64 p>
class fp {
    public:
    i64 x;
    fp() : x(0) {}
    fp(i64 x_) : x((x_ % p + p) % p) {}
    fp operator+() const { return fp(x); }
    fp operator-() const { return fp(-x); }
    fp& operator+=(const fp& y) {
        x += y.x;
        if (x >= p) x -= p;
        return *this;
    }
    fp& operator-=(const fp& y) { return *this += -y; }
    fp& operator*=(const fp& y) {
        x = x * y.x % p;
        return *this;
    }
    fp& operator/=(const fp& y) { return *this *= fp(inverse(y.x)); }
    fp operator+(const fp& y) const { return fp(x) += y; }
    fp operator-(const fp& y) const { return fp(x) -= y; }
    fp operator*(const fp& y) const { return fp(x) *= y; }
    fp operator/(const fp& y) const { return fp(x) /= y; }
    bool operator==(const fp& y) const { return x == y.x; }
    bool operator!=(const fp& y) const { return !(*this == y); }
    i64 extgcd(i64 a, i64 b, i64& x, i64& y) {
        i64 d = a;
        if (b != 0) {
            d = extgcd(b, a % b, y, x);
            y -= (a / b) * x;
        } else {
            x = 1;
            y = 0;
        }
        return d;
    }
    i64 inverse(i64 a) {
        i64 x, y;
        extgcd(a, p, x, y);
        return (x % p + p) % p;
    }
};

template <i64 p>
i64 abs(const fp<p>& x) { return x.x; }

template <i64 p>
ostream& operator<<(ostream& os, const fp<p>& x) {
    os << x.x;
    return os;
}

template <typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << ", " << p.second << ")";
    return os;
}

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
    os << "[";
    for (const auto& v : vec) {
        os << v << ",";
    }
    os << "]";
    return os;
}

template <typename T>
bool chmin(T& a, const T& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template <typename T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <typename A, typename T, size_t size>
void fill(A (&ary)[size], const T& val) {
    fill((T*)ary, (T*)(ary + size), val);
}

// x未満の要素の個数を返す
template <typename T>
i64 count_less(const vector<T>& v, T x) {
    return lower_bound(begin(v), end(v), x) - begin(v);
}

// x以下の要素の個数を返す
template <typename T>
i64 count_less_or_equal(const vector<T>& v, T x) {
    return upper_bound(begin(v), end(v), x) - begin(v);
}

// xより大きい要素の個数を返す
template <typename T>
i64 count_greater(const vector<T>& v, T x) {
    return end(v) - upper_bound(begin(v), end(v), x);
}

// x以上の要素の個数を返す
template <typename T>
i64 count_greater_or_equal(const vector<T>& v, T x) {
    return end(v) - lower_bound(begin(v), end(v), x);
}

// x未満の要素のうち最大のものを返す
template <typename T>
T max_less(const vector<T>& v, T x) {
    return *(lower_bound(begin(v), end(v), x) - 1);
}

// x以下の要素のうち最大のものを返す
template <typename T>
T max_less_or_equal(const vector<T>& v, T x) {
    return *(upper_bound(begin(v), end(v), x) - 1);
}

// xより大きい要素のうち最小のものを返す
template <typename T>
T min_greater(const vector<T>& v, T x) {
    return *upper_bound(begin(v), end(v), x);
}

// x以上の要素のうち最小のものを返す
template <typename T>
T min_greater_or_equal(const vector<T>& v, T x) {
    return *lower_bound(begin(v), end(v), x);
}

constexpr int inf = 1.01e9;
constexpr i64 inf64 = 4.01e18;
constexpr double eps = 1e-9;

template <class T>
T lower_gauss(T num, T den) {
    assert(den != 0);
    if (num == 0) return 0;
    if (num > 0 and den > 0) return num / den;
    if (num < 0 and den > 0) return (num - den + 1) / den;
    return lower_gauss(-num, -den);
}

template <class T>
T upper_gauss(T num, T den) {
    return lower_gauss(num, den) + (num % den == 0 ? 0 : 1);
}

void solve() {
    //constexpr i64 mod = 1'000'000'007;
    i64 N,K;
    cin >> N >> K;

    vector<i64> A(N);
    rep(i,0,N) cin >> A[i];

    vector<i64> ms,zs,ps;
    rep(i,0,N){
        if(A[i]<0) ms.emplace_back(A[i]);
        else if(A[i]==0) zs.emplace_back(A[i]);
        else ps.emplace_back(A[i]);
    }

    sort(begin(ms),end(ms));
    sort(begin(zs),end(zs));
    sort(begin(ps),end(ps));

    const i64 minus=ms.size(),zero=zs.size(),plus=ps.size();
    const i64 pminus=plus*minus,pzero=zero*(zero-1)/2+zero*(minus+plus),pplus=minus*(minus-1)/2+plus*(plus-1)/2;
    if(pminus>=K){
        auto ok=[&](i64 x){
            i64 sum=0;
            for(auto p : ps){
                const i64 y=lower_gauss(x,p);
                sum+=count_less_or_equal(ms,y);
            }
#ifdef  DEBUG
            i64 sum2=0;
            rep(i,0,N){
                rep(j,i+1,N){
                    if(A[i]*A[j]<=x) ++sum2;
                }
            }
            assert(sum==sum2);
#endif
            return sum>=K;
        };

        i64 lb=-inf64,ub=-1;
        assert(ok(ub));
        while(ub-lb>1){
            i64 mid=(lb+ub)/2;
            if(ok(mid)) ub=mid;
            else lb=mid;
        }

        cout << ub << endl;
    }else if(pminus+pzero>=K){
        cout << 0 << endl;
    }else{
        auto ok=[&](i64 x){
            i64 msum=0;
            for(auto m:ms){
                const i64 y=upper_gauss(x,m);
                msum+=count_greater_or_equal(ms,y); // z >= y
                if(m>=y) --msum;
            }
            msum/=2;

            i64 psum=0;
            for(auto p:ps){
                const i64 y=lower_gauss(x,p);
                psum+=count_less_or_equal(ps,y); // z <= y
                if(p<=y) --psum;
            }
            psum/=2;

            const auto sum=msum+psum;

#ifdef  DEBUG
            i64 sum2=0;
            rep(i,0,N){
                rep(j,i+1,N){
                    if(0<A[i]*A[j] and A[i]*A[j]<=x) ++sum2;
                }
            }
            assert(sum==sum2);
#endif
            return sum>=K-pminus-pzero;
        };

        i64 lb=0,ub=inf64;
        assert(ok(ub));
        while(ub-lb>1){
            i64 mid=(lb+ub)/2;
            if(ok(mid)) ub=mid;
            else lb=mid;
        }
        cout << ub << endl;
    }
}

int main() {
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    cout.setf(ios::fixed);
    cout.precision(16);
    solve();
    return 0;
}


Measured memory_bytes: 4084