let findBest best lowest next =
    let bestProfitCandidate = next - lowest
    if bestProfitCandidate > best then bestProfitCandidate else best

let maxProfit lst =
    let rec calcMaxProfit lowest best rem =
        match rem with
        | [] -> best
        | x::xs -> let lowest' = if x < lowest then x else lowest
                   calcMaxProfit lowest' (findBest best lowest x) xs
    let startLow = List.nth lst 0
    calcMaxProfit startLow 0 lst