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

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N,M; cin >> N >> M;
    vector<ll> D(M);
    rep(i,M) cin >> D[i];
    sort(D.begin(), D.end());

    ll ans = 2e9;
    rep(i,M) if(i + N - 1 < M) {
        // [D[i], D[i + N - 1]]
        ll L = D[i], R = D[i + N - 1];
        if(0 <= L) {
            ans = min(ans, R);
        } else if(R <= 0) {
            ans = min(ans, abs(L));
        } else {
            ans = min(ans, abs(L) + abs(R - L));
            ans = min(ans, abs(R) + abs(R - L));
        }
    }
    cout << ans << endl;
}