#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define ll long long
#define rep(i,n) for (int i = 0; i < (n); i++)
#define coutf(f) cout << fixed << setprecision(f)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()

int main() {
    int n, m;
    cin >> n >> m;
    vector<int> d(m);
    rep(i, m) cin >> d[i];
    sort(all(d));
    int ans = 1e9;
    for (int i = 0; i + n - 1 < m; i++) {
        int l = d[i];
        int r = d[i + n - 1];
        if (l * r > 0) ans = min(ans, max(abs(l), abs(r)));
        else ans = min(ans, abs(l) + abs(r) + min(abs(l), abs(r)));
    }
    cout << ans << endl;
    return 0;
}