#ifdef LOCAL111 #else #define NDEBUG #endif #include const int INF = 1e8; using namespace std; #define endl '\n' #define ALL(a) (a).begin(),(a).end() #define SZ(a) int((a).size()) #define FOR(i,a,b) for(int i=(a);i<(b);++i) #define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--) #define REP(i,n) FOR(i,0,n) #define RREP(i,n) for (int i=(n)-1;i>=0;i--) #define RBP(i,a) for(auto& i : a) #ifdef LOCAL111 #define DEBUG(x) cout<<#x<<": "<<(x)< void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;} template bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;} template bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;} typedef pair P; typedef long long int LL; typedef unsigned long long ULL; typedef pair LP; void ios_init(){ //cout.setf(ios::fixed); //cout.precision(12); #ifdef LOCAL111 return; #endif ios::sync_with_stdio(false); cin.tie(0); } int main() { ios_init(); int n,m; cin >> m >> n; vector d(n); REP(i,n) cin >> d[i]; sort(ALL(d)); int p = lower_bound(ALL(d),0)-d.begin(); int ans = INF; REP(i,n){ DEBUG(i); int cp = p; int cnt = 0; int dist = 0; if(d[i] < 0) cp--; int dir = (d[i] < 0 ? -1 : 1); DEBUG(dir); cnt = 1; dist += abs(d[cp]); int pre = d[cp]; int sp = cp; while(cnt < m){ DEBUG(cp); if(cp == i){ pre = d[sp]; dist = dist*2-d[sp]; cp = sp; dir *= -1; } cp += dir; if(!(0 <= cp and cp < n)){ DEBUG(1); break; } cnt++; dist += abs(pre-d[cp]); pre = d[cp]; } if(cnt == m) ans = min(ans,dist); DEBUG(ans), cout << endl; } cout << ans << endl; return 0; }