#include <bits/stdc++.h>
using namespace std;
#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

inline int power(int a, int b, int mod=M) {
    int x = 1;
    a %= mod;
    while (b) {
        if (b & 1) x = (x * a) % mod; 
        a = (a * a) % mod;
        b >>= 1;
    }
    return x;
}


//_ ***************************** START Below *******************************




vector<int> a;
int count(int n, int x){
	int ct = 0;
	int s = 0, e = 0;
	
	while(e<n && s<n-1){
		if(s==e) e++;
		if(a[e]-a[s] <= x){
			e++;
			ct += e-s;
		}
		else{
			s++;
		}
		
	}
	
	return ct;
}

int consistency(int n, int k){
	
	sort(begin(a), end(a));

	int s = 0, e = a[n-1]-a[0];
	
	while(s<e){
		int mid = s + (e-s)/2;
		if(count(n, mid) >= k){
			e = mid;
		}
		else s = mid+1;
	}
	
	return e;

}















int practice(int n, int k){


    return 0;
}





void solve() {
    
    int n, k;
    cin>> n >> k;
    
    a.resize(n);
    for(int i=0; i<n; i++) cin >> a[i];
    
    cout << consistency(n, k) << endl;


}





int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}