let n = stdin.ReadLine() |> int

let names =
    Array.init n (fun _ ->
        stdin.ReadLine().Split()
    )

let isUnique i x =
    names
    |> Array.mapi (fun j ys ->
           if i = j then
               true
           else
               ys
               |> Array.contains x
               |> not
       )
    |> Array.forall id

let haveUnique i xs =
    xs
    |> Array.exists (fun x -> isUnique i x)

let flg =
    names
    |> Array.mapi haveUnique
    |> Array.forall id

if flg then "Yes"
else "No"
|> printfn "%s"