int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n;
    int c;
    vi places;
    cin >> n >> c;

    FORI(n) {
        int input;
        cin >> input;
        places.push_back(input);
    }

    sort(places.begin(), places.end());

    int low = 1;
    int high = places[n - 1];

    while (low < high) {
        int mid = (high + low) / 2;
        bool suceed = true;
        int next = 0;

        FORI (c - 1) {
            int fb = -1;
            for (int i = next + 1; i < n; i++) {
                if (places[i] >= places[next] + mid) {
                    fb = i;
                    break;
                }
            }

            if (fb == -1) {
                suceed = false;
                break;
            }
            next = fb;
        }

        if (suceed)
            low = mid + 1;
        else
            high = mid;
    }
    cout << low - 1;
}