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; 2520 is the smallest number that can be divided by each of the numbers
; from 1 to 10 without any remainder.
; What is the smallest positive number that is evenly divisible by all
; of the numbers from 1 to 20?
extern printf
SECTION .data
flag: db "%d",10,0 ; "%d\n\0"
SECTION .text
global main
global is_divisible
main:
push rbp ; set up stack
mov rbp, rsp
mov rax, 2520 ; value to start at (given)
mov rcx, 20 ; divisor (counting down)
.loop add rax, rcx
push rcx
.isdiv xor rdx, rdx ; clear rdx for div
push rax ; save rax before dividing
div rcx ; rdx:rax/rcx = rax remainder rdx
pop rax ; reload rax to be divided again
cmp rdx, 0 ; the number was divisible, keep going
loopz .isdiv ; loop exits if rdx is non zero OR rcx is 0
cmp rcx, 0 ; if rcx = 0, it means it looped 20 to 1 w/o
jz .print ; any remainders, that's our number!
; if you get here, number couldn't be evenly divided by all numbers
pop rcx
jmp .loop
.print: mov rdi, flag ; arg 1 (format)
mov rsi, rax ; arg 2 (value)
mov rax, 0 ; no xmm registers
call printf wrt ..plt
pop rbp
mov rax, 0
ret
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