from machine import Pin
import time

rele = Pin(18, Pin.OUT)
led = Pin(21, Pin.OUT)
btn1 = Pin(25, Pin.IN, Pin.PULL_DOWN)
btn2 = Pin(26, Pin.IN, Pin.PULL_DOWN)
btn3 = Pin(12, Pin.IN, Pin.PULL_DOWN)
btn4 = Pin(14, Pin.IN, Pin.PULL_DOWN)
a = ""

while True:
    if btn1.value():
        a += "1"
        time.sleep(0.5)
    if btn2.value():
        a += "2"
        time.sleep(0.5)
    if btn3.value():
        a += "3"
        time.sleep(0.5)
    if btn4.value():
        a += "4"
        time.sleep(0.5)
    if "1243" == a:
        rele.value(1)
        for i in range(20):
            time.sleep(0.5)
            led.value(not led.value())
        rele.value(0)
        a = ""
    if len(a) > 4:
        a = ""
    print(a)