from machine import Pin
import time 
led=Pin(0,Pin.OUT)
led1=Pin(1,Pin.OUT)
led2=Pin(2,Pin.OUT)
while(1):
    led.on()
    led1.off()
    led2.off()
    time.sleep(3)
    led.off()
    led1.on()
    led2.off()
    time.sleep(3)
    led.off()
    led1.off()
    led2.on()
    time.sleep(3)
    led.off()
    led1.on()
    led2.off()
    time.sleep(3)