#include <bits/stdc++.h>

using namespace std;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

int N, M;
int D[1010];

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

    std::cin >> N >> M;

    for(int i=0;i<M;++i){
        std::cin >> D[i];
    }

    int res = 1001001001;
    for(int i=0;i<M;++i){
        for(int j=i+N-1;j<M;++j){
            int a = -min(D[i], 0),
                b = max(D[j], 0);
            
            res = min({res, 2 * a + b, a + 2 * b});
        }
    }

    std::cout << res << std::endl;
}