int leds[4] = {8, 9, 10, 11};

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

void loop() 
{

for (int i = 0; i<4; i++) {
  digitalWrite(leds[i], HIGH);
  delay(200);
}
for (int i = 0; i< 4; i++){
  digitalWrite(leds[i], LOW);
  delay(200);
}


}