let ``No.29 パワーアップ``() = let mutable itemSet = Set.empty let mutable powerUp = 0 [1.. (stdin.ReadLine() |> int) ] |> List.iter (fun i -> stdin.ReadLine().Split(' ') |> Array.map (int) |> Array.iter (fun n -> if itemSet.Contains n then powerUp <- powerUp + 1 itemSet <- (itemSet.Remove n) else itemSet <- (itemSet.Add n) ) ) powerUp <- powerUp + (itemSet.Count / 4) stdout.WriteLine powerUp ``No.29 パワーアップ``()