#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int max_dist(vector<int> &a, const int N)
{
    const int L = a.size();

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

    int min_d = 1;
    int max_d = (a[L - 1] - a[0]) / (N - 1);

    while (min_d <= max_d) {
        int d = min_d + (max_d - min_d) / 2;

        int count = 1;
        int last = 0;
        for (int i = 1; i < L; i++) {
            if (a[i] - a[last] >= d) {
                count++;
                last = i;
            }
        }

        if (count >= N) {
            min_d = d + 1;
        } else {
            max_d = d - 1;
        }
    }

    return max_d;
}

int main(void)
{
    int N, L;
    cin >> N >> L;

    vector<int> a(L);
    for (int i = 0; i < L; i++) {
        cin >> a[i];
    }

    cout << max_dist(a, N) << endl;
    
    return 0;
}