Reading and Printing User Entered MIPS Array - arrays

Question

So I am using MIPS trying to read in several strings entered by a user and then print them, but I am not getting the behavior I expect.
I want to take in 4 bytes of user input (4 characters essentially). In my loop I use the letter 'D' as a signal to exit. The problem is, no matter what I input, when I try to print the very first input later (or even the second, or the third), all I get printed out is the letter 'D' that was used to exit (which should be the last value of the array no?).
.data
mem: .space 256 #256 bytes of space for input
inst .space 5
.text
la $s1, mem #s1 used to take input
la $s2, 0($s1) #Pointer to base address of memory
jal readLoop #Read input loop
lw $a0, 0($s2) #Attempt to read very first saved input
li $v0, 4
syscall
li $v0, 10 #End program
syscall
readLoop:
li $v0, 8 #read string
la $a0, inst #location of input memory
addi $a1, $zero, 5 #length of buffer
syscall
lb $t2,($a0) #used to exit loop
sw $a0, 0($s1) #store input into memory
addi $s1, $s1, 4 #increment memory by 4 bytes
li $t1, 'D'
bne $t2, $t1, readLoop #exit loop on input of a 'D'
jr $ra
I've checked my input as it comes in and even when in the array after saving. It seems my print is the problem, but I could easily be wrong. Any ideas?

Answer 1

The fix was rather easy. Instead of storing the user input into a separate memory location and then putting that location in my array, I simply had the user input be stored directly into my array. See code changes below.
.data
mem: .space 256 #256 bytes of space for input
.text
la $s1, mem #s1 used to take input
jal readLoop #Read input loop
la $a0, mem #Attempt to read very first saved input
li $v0, 4
syscall
li $v0, 10 #End program
syscall
readLoop:
li $v0, 8 #read string
la $a0, mem #set user input as memory location
addi $a1, $zero, 5 #length of buffer
syscall
lb $t2,($a0) #used to exit loop
addi $s1, $s1, 4 #increment memory by 4 bytes
li $t1, 'D'
bne $t2, $t1, readLoop #exit loop on input of a 'D'
jr $ra