#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  vector<int> d(m);
  rep(i, m) cin >> d[i];
  sort(d.begin(), d.end());
  int ans = 1e9;
  rep(i, m - n + 1) {
    ans = min(ans, abs(d[i]) + (d[i + n - 1] - d[i]));
    ans = min(ans, abs(d[i + n - 1]) + (d[i + n - 1] - d[i]));
  }
  cout << ans << '\n';
  return 0;
}