volatile int currentLED = 0;//

int ledPins[] = {8, 9, 10, 11};

ISR(TIMER1_COMPA_vect)
{
  for(int i = 0; i < 4; i++)
  {
    digitalWrite(ledPins[i], LOW);
  }
  digitalWrite(ledPins[currentLED], HIGH);

  currentLED++;

  if(currentLED >= 4)
  {
    currentLED = 0;
  }
}

void setup()
{
  for(int i = 0; i < 4; i++)
  {
    pinMode(ledPins[i], OUTPUT);
  }

  noInterrupts();

  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;
  OCR1A = 15624;

  TCCR1B |= (1 << WGM12);

  TCCR1B |= (1 << CS12) | (1 << CS10);

  TIMSK1 |= (1 << OCIE1A);

  interrupts();
}

void loop()
{
}