module Sort_Module
    implicit none
    public
    contains
    recursive subroutine mergesort(a, p, r, b)
        integer(8) a(:), b(:)
        integer(8) p, r
        integer(8) q
        if (p < r) then
            q = (p+r)/2
            call mergesort(a, p, q, b)
            call mergesort(a, q+1, r, b)
            call merge(a, p, q, r, b)
        end if
    end subroutine mergesort
    subroutine merge(a, p, q, r, b)
        integer(8) a(:), b(:)
        integer(8) p, r, q, i, j, k
        integer(8) t
        k = p;   i = p;   j = q+1
        do
            if (.not. (k <= r)) exit
            if (j > r) then
                t = a(i);   i = i+1
            else if (i > q) then
                t = a(j);   j = j+1
            else if (a(i) <= a(j)) then
                t = a(i);   i = i+1
            else
                t = a(j);   j = j+1
            end if
            b(k) = t;   k = k+1
        end do
        do i = p, r
            a(i) = b(i)  
        end do
    end subroutine merge
    subroutine sort(a)
      integer(8) a(:),b(ubound(a,1)-size(a)+1:ubound(a,1)),n,k
      n = ubound(a,1)
      k = ubound(a,1)-size(a)+1
      call mergesort(a,k,n,b)
    end subroutine sort
    function POSL(a,v) result(r)!find first i:a(i)>=v
        implicit none
        integer(8) :: a(:),l,r,idx,v
        r = ubound(a,1) + 1
        l = ubound(a,1)-size(a)
        do while(r-l>1)
            idx = l + (r-l)/2
            if(a(idx) >= v)then
                r = idx
            else
                l = idx
            endif
        enddo
    end function
    function POSU(a,v) result(r)!find first i:a(i)>v
        implicit none
        integer(8) :: a(:),l,r,idx,v
        r = ubound(a,1) + 1
        l = ubound(a,1)-size(a)
        do while(r-l>1)
            idx = l + (r-l)/2
            if(a(idx) > v)then
                r = idx
            else
                l = idx
            endif
        enddo
    end function
    function NUM(a,v) result(n)
        implicit none
        integer(8) :: a(:),v,n
        n = POSU(a,v) - POSL(a,v)
    end function
end module Sort_Module
  

program atcoder
    use Sort_Module
    implicit none
    integer(8) :: ans,a,b,c(1:4),i,d(1:4)
    c=0
    do i=1,3
        read*,a,b
        c(a)=c(a)+1
        c(b)=c(b)+1
    enddo
    call sort(c)
    d(1)=1
    d(2)=1
    d(3)=2
    d(4)=2
    if( all(d==c) )then
        write(*,'(a)')"YES"
    else 
        write(*,'(a)')"NO"
    endif
    stop 
contains
end program atcoder