/// Problem 8 - Largest product in a series
///
/// Find the greatest product of five consecutive digits in the 1000-digit number.
///
/// 73167176531330624919225119674426574742355349194934
/// 96983520312774506326239578318016984801869478851843
/// 85861560789112949495459501737958331952853208805511
/// 12540698747158523863050715693290963295227443043557
/// 66896648950445244523161731856403098711121722383113
/// 62229893423380308135336276614282806444486645238749
/// 30358907296290491560440772390713810515859307960866
/// 70172427121883998797908792274921901699720888093776
/// 65727333001053367881220235421809751254540594752243
/// 52584907711670556013604839586446706324415722155397
/// 53697817977846174064955149290862569321978468622482
/// 83972241375657056057490261407972968652414535100474
/// 82166370484403199890008895243450658541227588666881
/// 16427171479924442928230863465674813919123162824586
/// 17866458359124566529476545682848912883142607690042
/// 24219022671055626321111109370544217506941658960408
/// 07198403850962455444362981230987879927244284909188
/// 84580156166097919133875499200524063689912560717606
/// 05886116467109405077541002256983155200055935729725
/// 71636269561882670428252483600823257530420752963450
///
/// Author: Vili Lähtevänoja
///

#time
let nStr = "73167176531330624919225119674426574742355349194934"
           + "96983520312774506326239578318016984801869478851843"
           + "85861560789112949495459501737958331952853208805511"
           + "12540698747158523863050715693290963295227443043557"
           + "66896648950445244523161731856403098711121722383113"
           + "62229893423380308135336276614282806444486645238749"
           + "30358907296290491560440772390713810515859307960866"
           + "70172427121883998797908792274921901699720888093776"
           + "65727333001053367881220235421809751254540594752243"
           + "52584907711670556013604839586446706324415722155397"
           + "53697817977846174064955149290862569321978468622482"
           + "83972241375657056057490261407972968652414535100474"
           + "82166370484403199890008895243450658541227588666881"
           + "16427171479924442928230863465674813919123162824586"
           + "17866458359124566529476545682848912883142607690042"
           + "24219022671055626321111109370544217506941658960408"
           + "07198403850962455444362981230987879927244284909188"
           + "84580156166097919133875499200524063689912560717606"
           + "05886116467109405077541002256983155200055935729725"
           + "71636269561882670428252483600823257530420752963450"
let ns =
    nStr.ToCharArray()
    |> Seq.ofArray
    |> Seq.windowed 13
    |> Seq.map ( fun a -> a|> Array.map (fun c -> int64(int(c) - int('0'))))
let products = ns |> Seq.map (fun x -> Array.fold (fun acc n -> acc*n) (int64(1)) x) 
let res = string(Seq.max products)
#time
printfn "%s" res 
