from machine import Pin
import time

led1 = Pin(18, Pin.OUT)
led2 = Pin(19, Pin.OUT)
led3 = Pin(21, Pin.OUT)

while True:
    led1.value(1)
    led2.value(0)
    led3.value(0)
    print("LED 1 ON, LED 2 OFF, LED 3 OFF")
    time.sleep(1)

    led1.value(0)
    led2.value(1)
    print("LED 1 OFF, LED 2 ON, LED 3 OFF")
    time.sleep(1)

    led1.value(0)
    led2.value(0)
    led3.value(1)
    print("LED 1 OFF, LED 2 OFF, LED 3 ON")
    time.sleep(1)