constexpr int DELAY_TIME = 3e3;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  if (!Serial) {
    Serial.println("SERIAL NOT OK");
  }
  for (int pinID = 3; pinID <= 5; pinID++) {
    pinMode(pinID, OUTPUT);
  }
}

int pinID = 3;
void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(pinID, HIGH);
  delay(DELAY_TIME);
  digitalWrite(pinID, LOW);
  pinID = pinID == 5 ? 3 : pinID + 1;
}