#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, in, f, l, j, ans = INF;
    vi d;
    cin >> n >> m;
    rep(i, 0, m) {
        cin >> in;
        d.push_back(in);
    }
    VSORT(d);
    if(d[0]>=0) ans = d[n-1];
    else {
        rep(i, n-1, m) {
            f = d[i-(n-1)];
            l = d[i];
            if(f<=0 && l>=0) ans = min(ans, min(abs(f)*2+l, abs(f)+l*2));
            else if(f>0) ans = min(ans, l);
        }
    }
    print(ans);
    return 0;
}