#define SW_PIN A5
#define SW_OFF 1

#define LED_PIN 12
#define LED_INTERVAL 1000

void setup() {
  // put your setup code here, to run once:
  pinMode(LED_PIN, OUTPUT);

  pinMode(SW_PIN, INPUT_PULLUP);
}

void loop() {
  while (digitalRead(SW_PIN) == SW_OFF) {
  }
  digitalWrite(LED_PIN, HIGH);
  delay(LED_INTERVAL);
  digitalWrite(LED_PIN, LOW);
  delay(LED_INTERVAL);
  digitalWrite(LED_PIN, HIGH);
  delay(LED_INTERVAL);
  digitalWrite(LED_PIN, LOW);
  delay(LED_INTERVAL);
}