def solve():
    N, M = map(int, input().split())
    L = []
    R = []

    for i in range(M):
        d = int(input())
        if d == 0:
            N -= 1
        elif d >= 0:
            R.append(d)
        else:
            L.append(-d)

    L.sort()
    R.sort()

    ans = 1e9

    for i in range(min(N, len(L))):
        l = L[i]
        if i == N - 1:
            ans = min(ans, l)
            continue
        ri = N - i - 2
        if len(R) > ri >= 0:
            r = R[N - i - 2]
            d = l * 2 + r
            ans = min(ans, d)

    for i in range(min(N, len(R))):
        r = R[i]
        if i == N - 1:
            ans = min(ans, r)
            continue
        li = N - i - 2
        if len(L) > li >= 0:
            l = L[N - i - 2]
            d = r * 2 + l
            ans = min(ans, d)

    print(ans)


if __name__ == '__main__':
    solve()