#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, n;
  cin >> k >> n;
  int a[500000], b[2][5000];
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  for (int i = 0; i < k; i++) b[0][i] = b[1][i] = 1000000000;
  b[0][0] = a[1] - a[0];
  if (n > 2)
    b[1][0] = min(a[2] - a[1], b[0][0]);
  else
    b[1][0] = 1000000000;
  for (int i = 3; i < n; i++) {
    int f = (i + 1) % 2;
    for (int j = min(i / 2, k - 1); j > 0; j--) {
      b[f][j] = min(min(b[0][j], b[1][j]), b[f][j - 1] + a[i] - a[i - 1]);
    }
    b[f][0] = min(min(b[0][0], b[1][0]), a[i] - a[i - 1]);
  }
  cout << min(b[0][k - 1], b[1][k - 1]);
  return 0;
}
