addi    $s5, $zero, 0
        #addi    $s4, $zero, 58
        lw      $t0, 0($a0)             # s0 = first
        lw      $t1, 4($a0)             # s1 = second
        lw      $t2, 8($a0)             # s2 = result
        lw      $t3, 12($a0)            # s3 = result length
        add     $s0, $t0, $zero
        add     $s1, $t1, $zero
        add     $s2, $t2, $zero
        add     $s3, $t3, $zero

        #addi    $s0, $s0, -1
        #addi    $s1, $s1, -1
        #addi    $s2, $s2, -1

        # add together, subtract, if > 57 carry
        addi    $t6, $s3, -1
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                    # jump to top