#include <bits/stdc++.h>
using namespace std;
template <class F> class y_combinator {
    F f;

   public:
    y_combinator(F&& f) : f(std::forward<F>(f)) {}
    template <class... Args> auto operator()(Args&&... args) const { return f(*this, std::forward<Args>(args)...); }
};
using ll = long long;
using ld = long double;
template <class T, class U = std::less<T>> using prique = std::priority_queue<T, std::vector<T>, U>;
template <class T> T floor(T a, T b) noexcept { return a / b - (a % b && (a ^ b) < 0); }
template <class T> T ceil(T a, T b) noexcept { return floor(a + b - 1, b); }
template <class T> bool chmin(T& x, const T& y) noexcept { return (x > y ? x = y, true : false); }
template <class T> bool chmax(T& x, const T& y) noexcept { return (x < y ? x = y, true : false); }
#define overload4(a, b, c, d, e, ...) e
#define rep1(a) for (long long _i = 0; _i < (a); _i++)
#define rep2(i, a) for (long long i = 0; i < (a); i++)
#define rep3(i, a, b) for (long long i = (a); i < (b); i++)
#define rep4(i, a, b, c) for (long long i = (a); i < (b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep(i, a, b, c) for (long long i = (a); i > (b); i += (c))
#define all(x) std::begin(x), std::end(x)
#define rall(x) std::rbegin(x), std::rend(x)
#define pb push_back
#ifndef LOCAL
#define debug(...)
#endif

void run_case() {
    int N, M;
    cin >> N >> M;
    vector<int> D(M);
    rep(i, M) cin >> D[i];
    sort(all(D));
    vector<int> A, B;
    int cur = 0;
    rep(i, M) {
        if (D[i] < 0) A.pb(-D[i]);
        else if (D[i] > 0) B.pb(D[i]);
        else cur++;
    }
    if (cur >= N) {
        cout << 0 << "\n";
    } else {
        reverse(all(A));
        vector<int> P(A.size() + 1);
        rep(i, A.size()) P[i + 1] = A[i];
        vector<int> Q(B.size() + 1);
        rep(i, B.size()) Q[i + 1] = B[i];
        int ans = 1e9;
        debug(P, Q);
        rep(i, 0, P.size()) {
            int j = N - cur - i;
            debug(i, j);
            if (j <= 0) {
                chmin(ans, P[i]);
            } else {
                if (j < Q.size()) chmin(ans, P[i] * 2 + Q[j]);
            }
        }
        rep(i, 0, Q.size()) {
            int j = N - cur - i;
            if(j <= 0) {
                chmin(ans, Q[i]);
            } else {
                if(j < P.size()) chmin(ans, Q[i] * 2 + P[j]);
            }
        }
        cout << ans << "\n";
    }
}
int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::fixed(std::cout).precision(16);
    int T = 1;
    while (T--) run_case();
    return 0;
}