let inpt = readLine()!.split(separator: " ").map{ Int($0)! }

let mustGet = inpt[0]
let itemCount = inpt[1]

var items = [Int]()

for _ in 0..<itemCount {
    items.append(Int(readLine()!)!)
}

items = items.sorted()

var ans = (items.last! - items.first!) + min(abs(items.last!), abs(items.first!))

for i in 0..<items.count {
    if i + mustGet > itemCount {
        break
    }
    let temp = abs(items[i + mustGet - 1] - items[i]) + min(abs(items[i + mustGet - 1]), abs(items[i]))
    ans = min(ans,temp)
}
print(ans)