let inputs = System.Console.ReadLine().Split(' ')
let args = seq{ for str in inputs do yield int(str) }

let matchPair a  b =
  match a,b with
  | a,b   when (a + 1) <=  b -> 0
  | a,b   when (a + 1) >   b -> (a + 1) - b
  | _,_   -> 0

let res = matchPair (Seq.head args) (Seq.item 1 args)
printfn "%s" (if res = 0 then "YES" else "NO")
printfn "%i" res