main = interact $ unlines . map (orthogonal . map (read::String->Double) . words) . lines
orthogonal [xa,ya,xb,yb,xc,yc,xd,yd] = if equal' (ab + cd) bd then "YES" else "NO"
 where
  ab = 1.0
  cd = 1.0
  bd = yc*10000
equal' x y = abs (x-y) < 0.000001