.model small 
.stack       
.data        
             

mes1 db 10,13,"Input a valid integer, please : ","$"
mes2 db 10,13,"Factorial is : ","$" 
dix         dw 10
acc         dw 0      
.code        
             
main   proc
	mov   ax,@data       
	mov   ds,ax         .
	
        mov   ah,09
	lea   dx,mes1     
        int   21h
        
        mov   ah,1
        int   21h
        add   al,48
        mov   ah,0
        mov   bx,ax
        
@1:      mov   ah,1
        int   21h
        mov   ah,0
        cmp   al,13
        je    @2
        add   al,-48
        
        mov   cx,9
        
        mov   dx,bx
@3:      add   dx,bx
        loop  @3
        mov   bx,dx
        add   bx, ax 
        jne @1
@2:      mov ah,2
        mov dl,10
        int 21h
        
        mov   ah,09
	lea   dx,mes2     
        int   21h       
        cmp  bx,0
        jne  suit1
        mov    ah,2
        mov    dx,bx
        int    21h  
suit1:  mov    cx,bx
        dec    cx
        mov    ax,1
calc:   mul    bx
        dec    bx
        loop   calc

@4:      cmp    ax,0
        je     @5
        mov    dx,0
        div    dix
        push   dx
        inc    acc
        jmp    @4
@5:      
        
        mov    cx,acc
@6:      pop    bx
        add    bl,48
        mov    ah,0
        ;add    bh,48
        mov    ah,2
        mov    dx,bx
        int    21h  
        loop   @6       
         
        mov   ax,4c00h  
	int   21h      

main   endp

end main