// No.370 道路の掃除
// https://yukicoder.me/problems/no/370
//

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int solve(vector<int> &D, unsigned int N);


int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    unsigned int N, M;
    cin >> N >> M;
    vector<int> D(M);
    for (int i = 0; i < M; ++i)
        cin >> D[i];
    int ans = solve(D, N);
    cout << ans << endl;
}

int solve(vector<int> &D, unsigned int N) {
    sort(D.begin(), D.end());
    int ans = 999999999;

    for (int s = 0; s <= D.size() - N; ++s) {
        int min_pos = D[s];
        int max_pos = D[s+N-1];
        if (min_pos * max_pos < 0) {
            ans = min(ans, abs(min_pos)*2 + abs(max_pos));
            ans = min(ans, abs(min_pos) + abs(max_pos)*2);
        } else {
            ans = min(ans, max(abs(min_pos), abs(max_pos)));
        }
    }
    return ans;
}