n, m = map(int, input().split())
minus = [0]
plus = [0]
for _ in range(m):
    d = int(input())
    if d > 0:
        plus.append(d)
    elif d == 0:
        n -= 1
    else:
        minus.append(-d)
if n <= 0:
    print(0)
    exit()
    
plus.sort()
minus.sort()
ans = 1 << 30
for i in range(n + 1):
    j = n - i
    if len(plus) <= i or len(minus) <= j:
        continue
    ans = min(ans, plus[i] + minus[j] + min(plus[i], minus[j]))
print(ans)