#include "bits/stdc++.h"
using namespace std;
#define fastcin {\
    cin.tie(0);\
    ios::sync_with_stdio(false);\
}
#define rep(i, a, b) for(int i = a; i < b; i++)
#define rrep(i, a, b) for(int i = a; i >= b; i--)
#define fore(i, a) for(auto &i:a)
#define print(x) cout << x << "\n"
#define SORT(a, n) sort(a, a+n);
#define REVERSE(a,n) reverse(a,a+n);
#define VSORT(v) sort(v.begin(), v.end());
#define VREVERSE(v) reverse(v.begin(), v.end());
#define MOD 1000000007
#define INF 1000000007
#define yes "YES"
#define no "NO"
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vll;

int main() {
    fastcin;
    int n, m, d, a = 0, b = 0, ans = 30000;
    bool dz = false;
    vi da, db;
    cin >> n >> m;
    rep(i, 0, m) {
        cin >> d;
        if(d==0) dz = true;
        else if(d>0) da.push_back(d);
        else db.push_back(-d);
    }
    if(dz) n--;
    VSORT(da);
    VSORT(db);
    int la = da.size(), lb = db.size();
    if(la>=n) ans = min(da[n-1], ans);
    if(lb>=n) ans = min(db[n-1], ans);
    if(la!=0 && lb!=0) {
        rep(i, 0, n) {
            if(da[a]<=db[b]) a++;
            else b++;
        }
        ans = min(min(da[a-1]*2+db[b-1], da[a-1]+db[b-1]*2), ans);
    }
    print(ans);
    return 0;
}