program main
  implicit none
  integer::N,L,i,time
  integer,allocatable::XWT(:,:)
  integer::X,W,T
  read *,N,L
  allocate(XWT(3,0:N))
  read *, XWT(:,1:N)

  XWT(:,0) = 0
  time     = 0
  do i=1,N
     W = XWT(2,i)
     T = XWT(3,i)

     time = time + XWT(1,i)-(XWT(1,i-1)+XWT(2,i-1))
     if(MOD(time,2*T).ge.0.and. &
        MOD(time,2*T).le.T-W     ) then
        time = time + W
     else
        time = time + 2*T-MOD(time,2*T) + W
     end if
  end do
  time = time + L - (XWT(1,N)+XWT(2,N))
  print '(i0)',time
end program main