N, M = map(int, input().split())

Dp = [0]
Dm = [0]

for _ in range(M):
    
    d = int(input())
    
    if d >= 0:
        
        Dp += [d]
        
    else:
        
        Dm += [-d]


Dp.sort()
Dm.sort()

print(min([Dp[i] + Dm[N - i] + min(Dp[i], Dm[N - i]) for i in range(max(0, N - len(Dm) + 1), min(N + 1, len(Dp)))]))