program main
  implicit none
  integer::N,i,j
  integer,parameter::len=111
  type match
     integer::r01,c01,r11,c11
  end type match
  type(match),allocatable::ml(:)
  integer::tab(len,len)
  data tab/12321*0/

  read *,N
  allocate(ml(N))
  read *,(ml(i),i=1,N)
  do i=1,N
     tab(ml(i)%r01,ml(i)%c01) = 1 + tab(ml(i)%r01,ml(i)%c01)
     tab(ml(i)%r11,ml(i)%c11) = 1 + tab(ml(i)%r11,ml(i)%c11)
  end do
  if(ANY(tab.gt.2)) then
     print '(a)',"NO"
  else
     print '(a)',"YES"
  end if

contains
  subroutine aprinter(array)
    integer*8::array(:)
    character*32::cformat='(i0,     (1x,i0))'
    write(cformat(5:9),'(i0)'),size(array)
    write(*,cformat) array
  end subroutine aprinter
end program main