let solve x =
    let n = Array.length x
    let mutable mn = 1000000000
    let mutable mx = -1000000000
    for i in 0 .. n - 2 do
        mn <- min mn (x.[i + 1] - x.[i])
        mx <- max mx (x.[i + 1] - x.[i])
    if mn = mx && mx <> 0 then "YES" else "NO"
        

let n = System.Console.ReadLine() |> int
let x = System.Console.ReadLine().Split() |> Array.map int |> Array.sort

System.Console.WriteLine(solve x)