open System

let No201 () =
    let A = Console.ReadLine().Split(' ')
    let B = Console.ReadLine().Split(' ')
    let Ap = int <| A.[1]
    let Bp = int <| B.[1]

    if Ap = Bp then
        printfn "-1"
    elif Ap < Bp then
        printfn "%s" B.[0]
    else
        printfn "%s" A.[0]

    ()

No201 ()