#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N, M;
  cin >> N >> M;
  vector<int> D(M), A, B;
  for (auto &&e : D) {
    cin >> e;
    if (e == 0) {
      N--;
    } else if (e > 0) {
      A.emplace_back(e);
    } else {
      B.emplace_back(-e);
    }
  }
  if (N <= 0) {
    cout << 0 << '\n';
    return 0;
  }
  A.emplace_back(0);
  B.emplace_back(0);
  sort(A.begin(), A.end());
  sort(B.begin(), B.end());
  int res = 1 << 30;
  for (int i = 0; i < N + 1; i++) {
    int j = N - i;
    if (i > (int)A.size() - 1 || j > (int)B.size() - 1) continue;
    int a = A[i], b = B[j];
    res = min(res, 2 * min(a, b) + max(a, b));
  }
  cout << res << '\n';
  return 0;
}