m,n=map(int,input().split())
x=[int(input()) for i in range(n)]
y=[[],[]]
for v in x:
	y[v>=0]+=[abs(v)]
for f in range(2):
	y[f]=[0]+sorted(y[f])
a=10**10
for i in range(m+1):
	for f in range(2):
		if i<len(y[f]) and m-i<len(y[f^1]):
			a=min(a,y[f][i]*2+y[f^1][m-i])
print(a)