let read() = stdin.ReadLine()
let reads() = read().Split() |> Array.map(int)

let X,Y = let t = reads() in t.[0],t.[1]
let N   = read() |> int
let A   = reads()

if N = 1 then
    true
else        
    let f a = Array.map (fun x -> (float x)/(float a))
    let mPassTime = A |> f Y 
    let kPassTime   = A |> f X
    let mPassTime = mPassTime.[1..]
    let kPassTime = kPassTime.[..(Array.length kPassTime)-2]    
    (mPassTime,kPassTime)
    ||> Array.forall2 (fun m k -> k <= m)
|> function |true -> "YES" | _ -> "NO"
|> printfn "%s"