let genSafeWord = 
    let cnt = ref 1    
    (fun (preWord:string) ->
        let preWord = preWord.ToCharArray()
        let preLastCharacter = preWord |> Array.last
        let addWord = 
            let w = (('a' |> int) + cnt.Value) |> char
            incr cnt
            if w = 'n' then  
                //nで終わるとoutになる
                let w =(('a' |> int) + cnt.Value) |> char
                incr cnt
                w
            else            
                w        
        let newWord = new string[|preLastCharacter;addWord|] 
        newWord) 

let genOutWord (preWord:string)=        
    let preWord = preWord.ToCharArray()
    let preLastCharacter = preWord |> Array.last
    let addWord = 'n'
    let newWord = new string[|preLastCharacter;addWord|] 
    newWord            

let startWord  = "aa"
let startChain = 0
let n = stdin.ReadLine() |> int

(startWord,startChain)
|> Seq.unfold (fun (word,chain)->
    match chain with
    | x when x = (n-1) -> 
        //n個目の単語はoutな単語を生成する
        let newWord = genOutWord word
        Some(word,(newWord,chain+1))
    | _ ->
        let newWord = genSafeWord word
        Some(word,(newWord,chain+1)))
|> Seq.skip 1
|> Seq.take n
|> Seq.iter(printfn "%s")