#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>

constexpr int INF = 1 << 30;

void solve() {
    int n, m;
    std::cin >> n >> m;

    std::vector<int> xs(m);
    for (auto& x : xs) std::cin >> x;
    std::sort(xs.begin(), xs.end());

    int ans = INF;
    for (int i = 0; i + n <= m; ++i) {
        int l = xs[i], r = xs[i + n - 1];
        ans = std::min(ans, r - l + std::min(std::abs(l), std::abs(r)));
    }

    std::cout << ans << std::endl;
}

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

    solve();

    return 0;
}