open System
type Sol() =
    member this.Solve() = 
        let N = stdin.ReadLine() |> int
        let S = Array.zeroCreate<string array> N
        for i = 0 to (N-1) do
            S.[i] <- stdin.ReadLine().Split();
        
        let checkRenchon (s :string [] []) j = 
            let mutable chk = true
            for i=0 to (N-1) do 
                if i <> j then (chk <- (chk && (s.[i].[j] = "nyanpass" )))
            chk
        
        let mutable cnt = 0
        let mutable idx = -1
        for i = 0 to (N-1) do 
            match (checkRenchon S i) with
            | true -> (cnt <- (cnt + 1) ;idx <- (i+1))
            | false -> ()
        
        printfn "%d" (if cnt = 1 then idx else -1)

let mySol = new Sol()
mySol.Solve()