from machine Import pin
from time Import sleep, sleep_ms

led1=pin(18,pin.out)
led2=pin(19,pin.out)
led3=pin(20,pin.out)
led4=pin(21,pin.out)

while true:
      led1.high()
      led2.high()
      led3.high()
      led4.high()
      sleep_ms(600)
      led1.low()
      led2.low()
      led3.low()
      led4.low()
      sleep_ms(600)