int yellow = 13;
int white = 12;


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

}

void loop() {
  // put your main code here, to run repeatedly:
    digitalWrite(yellow, HIGH);
    digitalWrite(white, LOW);
    delay(1000);

    digitalWrite(yellow, LOW);
    digitalWrite(white, HIGH);
    delay(1000);

}