from machine import Pin
import time 

print("Hello, Pi Pico!")

red = Pin(15, Pin.OUT)
yellow = Pin(14, Pin.OUT)
green = Pin(13, Pin.OUT)

while True:
    # RED 
    red.on()
    yellow.off()
    green.off()
    time.sleep(3)

    # YELLOW 
    red.off()
    yellow.on()
    green.off()
    time.sleep(1)

    # GREEN 
    red.off()
    yellow.off()
    green.on()
    time.sleep(3)

    # YELLOW 
    red.off()
    yellow.on()
    green.off()
    time.sleep(1)