void setup()
{
  pinMode(12, INPUT);
  pinMode(11, INPUT);
  pinMode(13, OUTPUT);
}

void loop()
{
  if (digitalRead(12) == HIGH) {
    while (!(digitalRead(11) == HIGH)) {
      digitalWrite(13, LOW);
      delay(1500); // Wait for 500 millisecond(s)
      digitalWrite(13, HIGH);
      delay(1500); // Wait for 500 millisecond(s)
    }
  }
  if (digitalRead(11) == HIGH) {
      digitalWrite(13, HIGH);
  }
}