#define FAST_ALLOCATOR_MEMORY 1e8
#include <vector>
#include <iostream>
#include <algorithm>
#include "optimization.h"
//#include <unordered_map>
//#include <cassert>
using namespace std;

int points[100'005];
int first_, last_;
int n;
bool is_in(int l, int r) { // [l, r]
    return last_ <= r and last_ >= l;
}

bool is(int ans, int k) {
    int cur_beg = first_;
    int cur_end = cur_beg + ans;
    int count = 1;
    if (is_in(cur_beg, cur_end)) return k >= count;
    while (true) {
        cur_beg = *upper_bound(points, points + n, cur_end);
        cur_end = cur_beg + ans;
        count++;
        if (count > k) return false;
        if (is_in(cur_beg, cur_end)) return k >= count;
    }
}
int main() {
    int k;
//    cin >> n >> k;
    n = readInt();
    k = readInt();
    for (int i = 0; i < n; i++) {
        int buf;
//        cin >> buf;
        buf = readInt();
        points[i] = buf;
    }
    sort(points, points + n);
    int right = points[n - 1];
    last_ = right;
    int left = points[0];
    first_ = left;
    int ans_right = right - left + 1;
    int ans_left = 0;
    while (ans_right > ans_left) {
        int ans_mid =  (ans_right + ans_left) / 2;
        if (is(ans_mid, k)) {
            ans_right = ans_mid;
        } else {
            ans_left = ans_mid + 1;
        }
    }
    writeInt(ans_left);
    writeChar('\n');
//    cout << ans_left << endl;
    return 0;
}