#define BUTTON 2

int pin_led[3] = {8, 9, 10};

void setup() {
  pinMode(BUTTON, INPUT);

  for (int x=0; x<3; x++) {
    pinMode(pin_led[x], OUTPUT);
  }
}

void loop() {
  if (digitalRead(BUTTON) == LOW) {
    for (int x=0; x<3; x++) {
      digitalWrite(pin_led[x], HIGH);
      delay(500);
    }

    for (int x=0; x<3; x++) {
      digitalWrite(pin_led[x], LOW);
      delay(500);
    }
  }
}