...
    call ReturnFreeRAM
    ld de,UserRAMEnd-UserRAM
    ld a,h
    ld c,l
    ld hl,0
    sll c ; unroll 16 times
    rla
    adc hl,hl
    sbc hl,de
    jr nc,$+4
    add hl,de
    dec c
    ld h,a
    ld l,c
    call DispDecHL
...