void setup() {
  pinMode(19, OUTPUT);
  pinMode(18, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(15, INPUT);
}

void loop() {
  if (digitalRead(15) == HIGH) {
    digitalWrite(19, HIGH);
    delay(500); 
    digitalWrite(19, LOW);
    
    digitalWrite(18, HIGH);
    delay(500);
    digitalWrite(18, LOW);
    
    digitalWrite(5, HIGH);
    delay(500);
    digitalWrite(5, LOW);
  } else {
    digitalWrite(19, LOW);
    digitalWrite(18, LOW);
    digitalWrite(5, LOW);   
  }
}