from machine import Pin
from time import sleep

led1=Pin(18,Pin.OUT)
led2=Pin(19,Pin.OUT)
led3=Pin(20,Pin.OUT)
led4=Pin(21,Pin.OUT)
while True:
    led1.value(1)
    sleep(1)
    led1.value(0)
    sleep(1)
    led3.value(1)
    sleep(1)
    led3.value(0)
    sleep(1)
    led2.value(1)
    sleep(1)
    led2.value(0)
    sleep(1)
    led4.value(1)
    sleep(1)
    led4.value(0)
    sleep(1)