long W = 2;

void setup() {

}

void loop() {
    for (int count = 0; count < 12; count++) {
      pinMode(W, OUTPUT);
       digitalWrite(W, 1);
      delay(500);
      pinMode(W, OUTPUT);
       digitalWrite(W, 0);
      W = W + 1;
    }
    for (int count = 0; count < 12; count++) {
      pinMode(W, OUTPUT);
       digitalWrite(W, 1);
      delay(500);
      pinMode(W, OUTPUT);
       digitalWrite(W, 0);
      W = W - 1;
    }

}