void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(14, OUTPUT); 
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(2, OUTPUT);
  pinMode(15, OUTPUT);
}

void loop() {
  digitalWrite(13,HIGH);
  digitalWrite(4,HIGH);
  delay(3000); //this spec
  digitalWrite(13,LOW);
  digitalWrite(4,LOW); 
  digitalWrite(12,HIGH);
  digitalWrite(2,HIGH);
  delay(3000);
  digitalWrite(12,LOW);
  digitalWrite(2,LOW);
  digitalWrite(14,HIGH);
  digitalWrite(15,HIGH);
  delay(3000);
  digitalWrite(14,LOW);
  digitalWrite(15,LOW);
  digitalWrite(12,HIGH);
  digitalWrite(2,HIGH);
  delay(3000);
  digitalWrite(12,LOW);
  digitalWrite(2,LOW);
  }