import itertools
N, M = map(int, input().split())
D = sorted([int(input()) for _ in range(M)])
ans = float('inf')
for i in range(M - N + 1):
    itr = list(itertools.islice(D, i, i+N, None))
    if itr[0] < 0 and itr[-1] >= 0:
        if abs(itr[0]) > abs(itr[-1]):
            move = abs(itr[-1]) * 2 + abs(itr[0])
            ans = min(ans, move)
        else:
            move = abs(itr[0]) * 2 + abs(itr[-1])
            ans = min(ans, move)
    elif itr[0] >= 0:
        ans = min(ans, abs(itr[-1]))
    else:
        ans = min(ans, abs(itr[0]))
print(ans)