let n = stdin.ReadLine () |> int

let arr =
    [|
        for _ in 0..n-1 ->
            let [|t; s|] = stdin.ReadLine().Split " "
            int t, s
    |]
    
let write: (int*string)*(int*string) -> int*string = function
    | (_, prev), (0, s) -> (0, prev + s)
    | (_, prev), (1, s) -> (1, s + prev)
    
let writeWrap a b =
    write (a, b)
    
Array.reduce writeWrap arr |> snd |> printfn "%s"