n, m = map(int, input().split())
D = [int(input()) for _ in range(m)]

D.sort()
ans = 10**18
res = 0
for i in range(m):
    res += abs(D[i])
    if i >= n - 1:
        if D[i - n + 1] <= 0 and D[i] >= 0:
            ans = min(ans, res + min(abs(D[i - n + 1]), D[i]))
        elif D[i] <= 0:
            ans = min(ans, abs(D[i - n + 1]))
        else:
            ans = min(ans, D[i])
        res -= abs(D[i - n + 1])
print(ans)