使用用户输入在mips中迭代添加数字。我试图在mips中将数字从1添加到用户的输入,但输出总是1

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.data
prompt:.asciiz "Enter a positive integer:"
I_msg1: .asciiz "(Iterarive) Sum from 1 to "
I_msg2: .asciiz " = "
R_msg1: .asciiz "(Recursive) Sum from 1 to "
R_msg2: .asciiz " = "
NewLine: .asciiz "\n"
NewLine2:.asciiz "\n\n"
done:.asciiz "Done..."


n : .word 0
result1: .word 0
result2: .word 0

.text 

.globl main
main:

    # Make two line space
    li $v0, 4
    la $a0,NewLine2
    syscall 
    # Print message to prompt user input
    li $v0, 4
    la $a0,prompt
    syscall 
    #read user input 
    li $v0, 5
    syscall
    #store user input in variable n
    sw $v0,n 
    #___________________________________
    #print I_msg1   
    li $v0,4
    la $a0,I_msg1
    syscall

    #print user input 
    li $v0,1
    lw $a0, n
    syscall

    #call iterative function 
    lw $a0,n
    jal ItrSum
    sw $v0, result1

    #Display I_msg2 
    li $v0, 4
    la $a0,I_msg2
    syscall 
    #print result of iterative sum
    li $v0,1
    lw $a0, result1
    syscall

    li $v0, 4
    la $a0,NewLine
    syscall 
    #______________________________

    #Exit 
    li $v0,10
    syscall

.globl ItrSum
    addi $sp, $sp, -4
    sw $s0,($sp)
    move $s0,$a0 #store value of n in $s0
ItrSum:
    beq $s0,$zero,end #if n = 0 end loop
    subi $t0,$s0,1 # find n-1 and store in new location t1
    add $t0,$s0,$t0 # n+(n-1)
    subi $s0,$s0,1  # decrement original  n 
    j ItrSum  #repeat

    end:
    add $v0, $s0,$v0 #store result in $v0
    lw $s0, ($sp)   
    addi $sp, $sp, 4 
    jr $ra