#define GREEN_LED PB9
#define RED_LED   PB6

void setup() {
  pinMode(GREEN_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
}

void loop() {
  
  digitalWrite(RED_LED, LOW);
  digitalWrite(GREEN_LED, HIGH);
  delay(500);
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(RED_LED, HIGH);
  delay(500);

}