#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int a[N];
int n, m;

bool check(int x)
{
    int st = 1, cnt = 1;
    for(int i = 2;i <= n;i++)
    {
        if(a[st] + x <= a[i])
        {
            st = i;
            cnt++;
        }   
    }
    if(cnt >= m)return true;
    return false;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> n >> m;
    for(int i = 1;i <= n;i++)
    cin >> a[i];
    sort(a + 1, a + 1 + n);

    int l = 1, r = 1e9;
    while(l < r)
    {
        int mid = (l + r + 1) >> 1;
        if(check(mid))l = mid;
        else r = mid - 1;
    }
    cout << l;
    return 0;
}