import sequtils, strutils

let
  n = parseInt readLine stdin
  xys = n.newSeqWith stdin.readLine.split.map parseInt

var ps = {2:8, 3:9, 7:9}

for v in xys:
  var x1, x2, y1, y2: int
  (x1, y1, x2, y2) = v
  if (x1, y1) in ps:
    let i = ps.find (x1, y1)
    ps[i] = (x2, y2)

echo ["NO", "YES"][ord ps == {5:8, 4:8, 6:8}]