#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
//int ax[] = {1, 2, 4, 8, 9};

//按照分布，检查是否能够排列即可
/*
  1、读入arr, mid
  2、按照分布排列，找到离mid格最近的槽位插入
 */
int check(const vector<int>& arr, int mid){
    if(arr.empty()) return 0;
    
    int cnt = 1;
    int n = arr.size();
    int dist = 0;
    for(int i = 1; i < n; ++i){
        dist += arr[i] - arr[i - 1];
        if(dist >= mid){
            cnt++;
            dist = 0;
        }
    }
    return cnt;
}

int main(){
    int n = 5, c = 3;
    cin >> n >> c;
    vector<int> arr(n);
    for(int i = 0; i < n; i++){
        cin >> arr[i];
        //arr[i] = ax[i];
    }
    sort(arr.begin(), arr.end());
    int smin = 0, smax = arr.back() - arr.front();
    //range [smin, smax], do mid to this range
    int l = smin, r = smax;
    int ans = 0;
    while(l <= r){
        int mid = (l+r)/2;
        int cc = check(arr, mid);
        if (cc >= c) {
            ans = mid;
            l = mid + 1;
        } else r = mid - 1;
    }
    cout << ans << endl;
    return 0;
}