let args2 = [ 3;4 ]
  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,_ -> 0
      | _,0 -> 0


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