#include <iostream>
#include <cstdio>
#include <algorithm>
#include <climits>

using namespace std;

int N, M, D[1000];

void solve() {
    scanf("%d %d", &N, &M);
    for (int i = 0; i < M; i++) scanf("%d", &D[i]);
    sort(D, D + M);
    int ans = INT_MAX;
    for (int i = 0; i < M - N + 1; i++) {
        if (D[i + N - 1] <= 0) ans = min(ans, -D[i]);
        else if (D[i] >= 0) ans = min(ans, D[i + N - 1]);
        else ans = min(ans, min(-D[i], D[i + N - 1]) * 2 + max(-D[i], D[i + N - 1]));
    }
    printf("%d\n", ans);
}

int main() {
    solve();
    return 0;
}