import time
from machine import Pin
led = Pin(2, Pin.OUT)
led1 = Pin(4, Pin.OUT)
led2 = Pin(5, Pin.OUT)
led3 = Pin(18, Pin.OUT)

while True:
    led.value(1)
    led1.value(0)
    led2.value(1)
    led3.value(0)
    time.sleep(0.5)
    led.value(0)
    led1.value(1)
    led2.value(0)
    led3.value(1)
    time.sleep(0.5)