unsigned long prevMillis = 0;
const long interval = 5000;
const int led = 13;

void setup() {
  Serial.begin(9600);
  Serial.println("Hello World");
  pinMode(led, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();
  Serial.println(currentMillis);
  digitalWrite(led, 0);
  if (currentMillis - prevMillis >= interval) {
    prevMillis = currentMillis;
    Serial.println(prevMillis);
    digitalWrite(led, 1);
  }
}