n, m = map(int, input().split())
d = sorted([int(input()) for i in range(m)])
res = 10 ** 18
for i in range(m - n + 1):
  l, r = d[i], d[i + n - 1]
  if (l * r >= 0):
    res = min(res, max(abs(l), abs(r)))
  else:
    res = min(res, abs(l) * 2 + abs(r))
    res = min(res, abs(l) + abs(r) * 2)
print(res)