from machine import Pin
import time

led1 = Pin(23, Pin.OUT)
led2 = Pin(22, Pin.OUT)
led3 = Pin(21, Pin.OUT)
led4 = Pin(19, Pin.OUT)


while 1:
    led1.value(1)
    time.sleep_ms(500)
    led1.value(0)
    led2.value(1)
    time.sleep_ms(500)
    led2.value(0)
    led3.value(1)
    time.sleep_ms(500)
    led3.value(0)
    led4.value(1)
    time.sleep_ms(500)
    led4.value(0)