#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountll((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzll(x))
#define rep(i, n) for(int i = 0; i < n; i++)
const int inf9 = 1e9; const lint inf18 = 1e18;
template<class T> inline void YES(T condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class T = string, class U = char>int character_count(T text, U character){ int ans = 0; for(U i: text){ ans += (i == character); } return ans; }
lint power(lint base, lint exponent, lint module){ if(exponent % 2){ return power(base, exponent - 1, module) * base % module; }else if(exponent){ lint root_ans = power(base, exponent / 2, module); return root_ans * root_ans % module; }else{ return 1; }}
struct position{ double y, x; }; position mv[4] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}}; double euclidean(position first, position second){ return sqrt((second.x - first.x) * (second.x - first.x) + (second.y - first.y) * (second.y - first.y)); } double euclidean(double first, double second){ return sqrt(first * first + second * second); }
template<class T, class U> string to_string(pair<T, U> x){ return to_string(x.first) + "," + to_string(x.second); } string to_string(string x){ return x; }
template<class itr> void array_output(itr start, itr goal){ string ans; for(auto i = start; i != goal; i++) ans += to_string(*i) + " "; if(!ans.empty()) ans.pop_back(); cout << ans << endl; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class T> T gcd(T a, T b){ if(a && b){ return gcd(min(a, b), max(a, b) % min(a, b)); }else{ return a; }} template<class T> T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct combination{ vector<lint> fact, inv; combination(int sz) : fact(sz + 1), inv(sz + 1){ fact[0] = 1; for(int i = 1; i <= sz; i++){ fact[i] = fact[i - 1] * i % mod; } inv[sz] = power(fact[sz], mod - 2, mod); for(int i = sz - 1; i >= 0; i--){ inv[i] = inv[i + 1] * (i + 1) % mod; } } lint P(int n, int r){ if(r < 0 || n < r) return 0; return (fact[n] * inv[n - r] % mod); } lint C(int p, int q){ if(q < 0 || p < q) return 0; return (fact[p] * inv[q] % mod * inv[p - q] % mod); } };
template<class itr> bool next_sequence(itr first, itr last, int max_bound){ itr now = last; while(now != first){ now--; (*now)++; if((*now) == max_bound){ (*now) = 0; }else{ return true; } } return false; }
template<class itr, class itr2> bool next_sequence2(itr first, itr last, itr2 first2, itr2 last2){ itr now = last; itr2 now2 = last2; while(now != first){ now--, now2--; (*now)++; if((*now) == (*now2)){ (*now) = 0; }else{ return true; } } return false; }
inline int at(lint i, int j){ return (i >> j) & 1; }

int main(){
    int N;
    lint K;
    cin >> N >> K;
    lint zero = 0;
    vector<lint> minus, plus;
    for(int i = 0; i < N; i++){
        lint A;
        cin >> A;
        if(A == 0){
            zero++;
        }else if(A < 0){
            minus.push_back(-A);
        }else{
            plus.push_back(A);
        }
    }
    sort(all(minus));
    sort(all(plus));
    lint low = -2e18, high = 2e18; // (low, high]
    while(low + 1 < high){
        lint mid = (low + high) / 2;
        lint ans = 0;
        if(mid >= 0){
            ans += zero * (N - zero) + zero * (zero - 1) / 2;
            ans += minus.size() * plus.size();
            for(int i = 0; i < minus.size(); i++){
                int right = int(upper_bound(all(minus), mid / minus[i]) - minus.begin() - i);
                    right--;
                ans += max(0, right);
            }
            for(int i = 0; i < plus.size(); i++){
                int right = int(upper_bound(all(plus), mid / plus[i]) - plus.begin() - i);
               // if(mid / plus[i] >= plus[i]){
                    right--;
               // }
                ans += max(0, right);
            }
        }else{
            mid = -mid;
            for(int i = 0; i < plus.size(); i++){
                int right = int(minus.end() - lower_bound(all(minus), (mid + plus[i] - 1) / plus[i]));
                ans += max(0, right);
            }
            mid = -mid;
        }
        //cout << low << " " << high << " " << mid << " -> " << ans << endl;
        if(ans >= K){
            high = mid;
        }else{
            low = mid;
        }
    }
    cout << high << endl;
}


Measured memory_bytes: 2420