open System open System.Collections.Generic [] module Cin = let read f = stdin.ReadLine() |> f let reada f = stdin.ReadLine().Split() |> Array.map f let readChars() = read string |> Seq.toArray let readInts() = readChars() |> Array.map (fun x -> Convert.ToInt32(x.ToString())) [] module Cout = let writer = new IO.StreamWriter(new IO.BufferedStream(Console.OpenStandardOutput())) let print (s: string) = writer.Write s let println (s: string) = writer.WriteLine s let inline puts (s: ^a) = string s |> println // ----------------------------------------------------------------------------------------------------- module Prime = let inline isPrime (n: int) = let limit = n |> float |> sqrt |> int seq { for p in 2 .. limit do if n % p = 0 then yield () } |> Seq.isEmpty /// nを素因数分解した結果を返す let primeFactors (n: int64): Map = let limit = n |> float |> sqrt |> int64 let rec count x p acc = if x % p = 0L then count (x / p) p (acc + 1L) else acc let mutable n = n let res = seq { for p in 2L .. limit + 1L do let c = count n p 0L if c <> 0L then let div = (float p) ** (float c) |> int64 n <- n / div yield (p, c) } |> Map.ofSeq if n = 1L then res else res.Add(n, 1L) /// nの約数の個数 let divisorsCount (n: int64): int64 = primeFactors n |> Map.fold (fun acc k v -> acc * (v + 1L)) 1L /// upper以下の素数を列挙 let sieveToUpper upper = seq { yield 2 let knownComposites = System.Collections.Generic.SortedSet() for i in 3 .. 2 .. upper do let found = knownComposites.Contains(i) if not found then yield i for j in i .. i .. upper do knownComposites.Add(j) |> ignore } /// 添え字が素数かどうかを表す配列を返す let eraSieve upper = let upper = int upper + 1 let res = Array.init upper (fun _ -> true) res.[0] <- false res.[1] <- false let rec loop a b = let c = a * b if c >= upper then () else res.[c] <- false loop a (b + 1) for i in 2 .. upper - 1 do if res.[i] then loop i 2 res /// nの約数を列挙(n自身を含む) /// O(log n) let divisors (n: int64): int64 array = let lim = n |> float |> sqrt |> int64 seq { for i in 1L .. lim do if n % i = 0L then yield i if i * i <> n then yield n / i } |> Array.ofSeq |> Array.sort // ----------------------------------------------------------------------------------------------------- let main() = let [| n; L |] = reada int let sieve = Prime.eraSieve L let rec loop i (acc: int64) = if i > L then acc else if sieve.[i] then let r = (n - 1) * i if r > L then acc else let t = int64 L - int64 r + 1L loop (i + 1) (acc + t) else loop (i + 1) acc loop 0 0L |> puts () // ----------------------------------------------------------------------------------------------------- main() writer.Dispose()