fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)

fun readStr () =
    let
        fun scan reader stream = SOME (StringCvt.splitl (not o Char.isSpace) reader (StringCvt.skipWS reader stream))
    in
        valOf (TextIO.scanStream scan TextIO.stdIn)
    end


fun member x nil = false
  | member x (h::tl) =
    if x = h
    then true
    else member x tl

fun asSet nil = nil
  | asSet (h::tl) = 
    let
        val set' = asSet tl
    in
        if member h set'
        then set'
        else h :: set'
    end


val () =
    let
        val n = readInt ()
        val s = readStr ()

        val set = asSet (String.explode s)
        val ans = if List.length set = n then "No"
                  else "Yes"              
    in
        print (ans ^ "\n")
    end