;exportar label de inicio do programa
global _start

section .data		;seccao data - dados inicializados 

; variaveis de 32 bits
m:	dd 5
n:	dd 3
res:	dd 0

section .text		;seccao text - codigo

_start: nop

; Implemente uma subrotina (comb) que calcula C(m,n),
; recorrendo a chamadas à subrotina factorial implementada
; anteriormente.

	push	dword [m]
	push	dword [n]
	call	comb
	add	esp, 8
	mov	[res], eax

; chamada ao sistema para terminar o programa
	mov 	eax, 1		;codigo de "exit"
	mov	ebx, 0		;valor retornado ao sistema
	int	0x80		;chamda ao sitema


comb:	; ebp + 12 = m
	; ebp + 8 = n
	push	ebp
   	mov 	ebp, esp
	push	ebx
	sub	esp, 2*4	;ebp - 4 = m!
				;ebp - 8 = n!

			;calcular m!
   	push	dword	[ebp + 12]
	call	factorial
	add	esp, 4
	mov	[ebp - 4], eax	;save m!	
				;calcular n!
   	push	dword	[ebp + 8]
	call	factorial
	add	esp, 4
	mov	[ebp - 8], eax	;save n!	
				;calcular (m - n)!
	mov	eax, [ebp + 12]
	sub	eax, [ebp + 8]
   	push	eax
	call	factorial
	add	esp, 4
	
	mov	ebx, [ebp - 8]
	mul	ebx
	mov	ebx, [ebp - 4]
	xchg	eax, ebx
	div	ebx

	add	esp, 2*4
	pop	ebx
   	pop	ebp
 	ret


factorial:
	push	ebp
   	mov 	ebp, esp
	push	ebx

   	mov 	ebx, [ebp + 8]	
	mov	eax, ebx
  loop: 
	dec	ebx
	cmp	ebx, 1
	jle	endfact
	imul	ebx
	jmp 	loop
   endfact:
	pop	ebx
   	pop	ebp
 	ret