main = interact $ unlines . map (orthogonal . map read . words) . lines
orthogonal [xa,ya,xb,yb,xc,yc,xd,yd] = if equal' (ab + cd) bd then "YES" else "NO"
 where
  ab = 1
  cd = 1
  bd = 1
equal' x y = abs (x-y) < 0.000001