let n = stdin.ReadLine() |> int

let arr = stdin.ReadLine().Split()

let mutable flg = false

if arr.[0] = arr.[1] then
    flg <- true
elif n > 2 then
    for i = 2 to n - 1 do
        if arr.[i] = arr.[i - 1] then
            flg <- true
        if arr.[i] = arr.[i - 2] then
            flg <- true

if flg then
    "Yes"
else
    "No"
|> printfn "%s"