void setup() {
  // put your setup code here, to run once:
  pinMode(2, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(16, OUTPUT);
  pinMode(17, OUTPUT);
  pinMode(18, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(2, HIGH);
  delay(500);
  digitalWrite(2, LOW);
  delay(500);
  digitalWrite(4, HIGH);
  delay(500);
  digitalWrite(4, LOW);
  delay(500);
  digitalWrite(16, HIGH);
  delay(500);
  digitalWrite(16, LOW);
  delay(500);
  digitalWrite(17, HIGH);
  delay(500);
  digitalWrite(17, LOW);
  delay(500);
  digitalWrite(18, HIGH);
  delay(500);
  digitalWrite(18, LOW);
  delay(500);
}