#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    
    int N,M;
    cin >> N >> M;
    vector<long long> V(M);
    for ( int i = 0; i < M; i++ ) {
        cin >> V[i];
    }
    long long ans = LLONG_MAX;
    for ( int i = 0; i <= M-N; i++ ) {
        long long a;
        long long x = V[i]; long long y = V[i+N-1];
        if ( x*y >= 0 ) { a = max( abs(x), abs(y) ); }
        else { a = min(abs(x),abs(y))*2 + max(abs(x),abs(y)); }
        ans = min( ans, a );
    }
    cout << ans << endl;
    return 0;
}