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 intString n =
    if 0 <= n
    then Int.toString n
    else "-" ^ Int.toString (abs n)


fun tally limit index l =
    if index = limit then []
    else
        (
          (index,
           List.foldl
               (fn (arr, acc) =>
                   if Array.sub (arr, index) = "nyanpass" then acc + 1
                   else acc)
               0
               l
          )
          ::
          (tally limit (index + 1) l)
        )


fun findAns n ls =
    let
        val withIndex = tally n 0 ls
        val filtered =
            List.filter
                (fn (_, x) =>
                    x = n - 1)
                withIndex
    in
        if List.length filtered = 1 then #1 (List.hd filtered) + 1
        else ~1
    end


val () =
    let
        val n = readInt ()
        val a_s = List.tabulate (n, fn _ => Array.fromList (List.tabulate (n, fn _ => readStr ())))
        val ans = findAns n a_s
    in
        print (intString ans ^ "\n")
    end