void setup() {
  // put your setup code here, to run once:
  DDRB |= 1 <<4;
    DDRB |= 1 <<3;
}

void loop() {
  // put your main code here, to run repeatedly:
  PORTB |= 1 <<4;
  PORTB &= ~(1<<3);
  delay(500);
  PORTB &= ~(1<<4);
  PORTB |= 1 <<3;
  delay(500);
}