def main():
    N, M = map(int, input().split())
    l = [int(input()) for _ in range(M)]

    if 0 not in l:
        N += 1
        l.append(0)

    l.sort()
    ans = 10 ** 10
    for i in range(len(l) - N):
        a = l[i:i + N]
        if 0 not in a:
            continue
        m = [i for i in a if i < 0]
        p = max(a)
        if m:
            if abs(min(m)) < p:
                ans = min(ans, abs(min(m)) * 2 + p)
            else:
                ans = min(ans, abs(min(m)) + p * 2)
        else:
            ans = min(ans, p)

    print(ans)

if __name__ == '__main__':
    main()