loop:
        bltz    $t6, end                # finish if t6 is < 0
        #beq     $s5, $s3, end
        add     $s0, $s0, $t6
        add     $s1, $s1, $t6
        add     $s2, $s2, $t6
        #add     $s2, $s0, $s1
        lb      $t3, 0($s0)
        lb      $t4, 0($s1)
        addi    $t3, $t3, -48
        addi    $t4, $t4, -48
        add     $t5, $t3, $t4            # t5 = result of addition
        #slti    $s6, $t5, 10             # if s2 < 58, s6=1
        #beq     $s6, $zero, carry        # carry if s2=58 or is >
        #add     $s2, $s1, $s0           # otherwise, just add
        addi    $t5, $t5, 48
        sb      $t5, 0($s2)
        addi    $t6, $t6, -1            # subtract 1 from t6
        j       loop