.text
.org 0x20

stev1:  .byte   10
stev2:  .byte   5
rez:    .space  1

.align

.global _start
_start:

  adr   r0, stev1
  ldrb  r1, [r0]

  adr   r0, stev2
  ldrb  r2, [r0]

  sub   r1, r2

  adr   r0, rez
  str   r1, [r0]