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 let main() = let n = read int let maze = Array2D.init n n (fun _ _ -> 0) let mutable d = 0 let nextD() = d <- (d + 1) % 4 let mutable (x, y) = (0, 0) let step x y = match d with | 0 -> x + 1, y | 1 -> x, y + 1 | 2 -> x - 1, y | _ -> x, y - 1 let isOut x y = not (0 <= x && x < n && 0 <= y && y < n) for i in 0 .. n * n - 1 do let a = i + 1 maze.[y, x] <- a let mutable (nx, ny) = step x y if isOut nx ny then nextD() let a, b = step x y nx <- a ny <- b if maze.[ny, nx] <> 0 then nextD() let a, b = step x y nx <- a ny <- b x <- nx y <- ny for i in 0 .. n - 1 do let s = maze.[i, *] |> Array.map (fun x -> sprintf "%03d" x) String.Join(" ", s) |> puts main() writer.Close()