from machine import Pin
from utime import sleep

led1 = Pin(15, Pin.OUT)
led2 = Pin(16, Pin.OUT)
led3 = Pin(17, Pin.OUT)
while True:
  led1.on()
  led2.off()
  led3.off()
  sleep(1)
  led1.off()
  led2.on()
  led3.off()
  sleep(1)
  led1.off()
  led2.off()
  led3.on()
  sleep(1)